Free-space communication based on quantum cascade laser

Chuanwei Liu; Shenqiang Zhai; Jinchuan Zhang; Yuhong Zhou; Zhiwei Jia; Fengqi Liu; Zhanguo Wang

doi:10.1088/1674-4926/36/9/094009

J. Semicond. > 2015, Volume 36 > Issue 9 > 094009

SEMICONDUCTOR DEVICES

Free-space communication based on quantum cascade laser

Chuanwei Liu, Shenqiang Zhai, Jinchuan Zhang, Yuhong Zhou, Zhiwei Jia, Fengqi Liu and Zhanguo Wang

+ Author Affiliations

Corresponding author: Zhai Shenqiang, zsqlzsmbj@semi.ac.cn

DOI: 10.1088/1674-4926/36/9/094009

Abstract: A free-space communication based on a mid-infrared quantum cascade laser (QCL) is presented. A room-temperature continuous-wave distributed-feedback (DFB) QCL combined with a mid-infrared detector comprise the basic unit of the communication system. Sinusoidal signals at a highest frequency of 40 MHz and modulated video signals with a carrier frequency of 30 MHz were successfully transmitted with this experimental setup. Our research has provided a proof-of-concept demonstration of space optical communication application with QCL. The highest operation frequency of our setup was determined by the circuit-limited modulation bandwidth. A high performance communication system can be obtained with improved modulation circuit system.

Key words: quantum cascade laser, free-space communication, video transmission

1. Introduction

Free-space optical (FSO) systems are promising networking solutions for broadband communication technologies due to their clear advantages,such as unlimited bandwidth (no RF spectrum licensing),low cost,high security and mobility^{[1, 2, 3, 4]}. As the most optimum light source in the infrared wavelength range,quantum cascade lasers (QCLs) present a huge potential for the application in this field^{[5, 6, 7]}. For one thing,their emission wavelengths are typically in the so-called atmospheric window regions,i.e.,3-5 $\mu$ m and 8-14 $\mu$ m. Thus the radiation suffers less attenuation than shorter wavelength light from near-infrared (NI) lasers,which permits rather longer propagation distance even in adverse weather conditions^[8]. For another,the fast internal lifetimes of these devices allow for high operating and modulation frequency of up to 5-10 GHz^[5],which promise very high communication bandwidth. In addition,FSO based on mid-IR QCLs is far more secure because of technological barriers to the high performance infrared detectors,making laser beams harder to detect and even harder to intercept and crack. Therefore the applications of QCLs for FSO have attracted more and more research and commercial interests^{[10, 11, 12]},especially as the QCL technology has become gradually mature in recent years. The continuous-wave room-temperature high-speed devices have paved the way for the wide use of QCL in FSO area.

In this paper,a free-space mid-infrared communication setup based on a home-made QCL in our research group is constructed to provide a proof-of-concept demonstration of space optical communication application with QCL. The laser is a room-temperature continuous-wave operation of DFB device emitting at 4.7 $\mu$ m. A HgCdTe detector operating at room temperature with peak response wavelength of about 5 $\mu$ m is used to receive light. Sinusoidal signals at a highest frequency of 40 MHz and modulated video signals with a carrier frequency of 30 MHz were successfully transmitted with this experimental setup. The highest operation frequency of our setup was determined by the circuit-limited modulation bandwidth. A high performance communication system can be obtained with improved modulation circuit and optical optimization system.

2. FSO communication system

2.1 Laser and detector

The laser used in this experiment was grown by molecular beam epitaxy (MBE) in the InGaAs/InAlAs material system. The active region is designed based on the so-called double-resonant-phonon. The laser chip,consisting of 2-mm-long,10- $\mu$ m-wide deep etched ridge is epilayer-down bonded to a copper heat sink. The laser was packaged in a HHL (high heat load) and collimated by an optic lens inside the package,as illustrated in the inset of . The device can operate in room-temperature continuous-wave (CW) mode emitting around 4.7 $\mu$ m. Figure 1 shows the photoelectric properties of the device. The threshold current of the QCL is about 300 mA. In the experiment,DC-bias current was set at about 350 mA with about 12 mW output power.

Figure Fig1. Power-current-voltage curve of the QCL. The picture on the upper left corner is the laser employed in the experiment.

DownLoad: Full-Size Img PowerPoint

The HgCdTe detector in our setup is bought from VIGO (PVMI-10.6) and has a peak response at about 5 $\mu$ m. It has a response time shorter than 1 ns,which can satisfy the frequency requirement in our experiment. However,the detector operated under photovoltaic mode,which limited the responsivity and requires higher light power in the experiment. Normalized spectra of the laser emission and the detector response are demonstrated in Figure 2. It is clear that the detector can easily detect the emission light of the laser.

Figure Fig2. Normalized spectra of the laser emission and the detector response.

DownLoad: Full-Size Img PowerPoint

2.2 Experimental technique

A schematic of the experimental setup is shown in . The input signals to be transmitted,i.e.,sinusoidal signals and modulated video signal,and DC current are synthesized to drive the laser through a bias-T. The sinusoidal signals are provided by a function generator,while the modulated video signal is from a camera and modulated by a home-made modulator. Being well packaged,it is not necessary to collimate the emitted radiation from the device again. Using two plane mirrors,the radiation is guided along a 2.5 m optical path in the air,and then focused onto the detector with a CaF $_{2}$ optical lens. The 2.5 m range is limited by the length of the optical table where the emitter and receiver are fixed. However in the practical application for long-distance transmission,the laser beam needs to be perfectly collimated with a collimating beam expanding system. The electrical signal from the detector was amplified by a low-noise-amplifier (LNA) and then added to a home-made demodulator. After demodulation,the transmitted signals can be examined with an oscilloscope. In addition,the video signal can be displayed with an LCD screen to test the communication quality visually.

Figure Fig3. Scheme of FSO communication system.

DownLoad: Full-Size Img PowerPoint

3. Results and discussions

Sinusoidal signals with different frequencies generated by the signal generator were transmitted through the link. The time traces of the input signals and received signals are shown in Figure 4. The received signals show a clear phase shift compared with input ones,which is caused by the amplifier circuits and the response time of the detector. At 20 MHz,the waveform of the received signal is in good accordance with the input signal. However the signal-to-noise ratio is not so good,which can be attributed to the low responsivity of the photovoltaic detector and high noise from the circuits. A detector with higher responsivity and a high-pass filter to eliminate the low frequency noise will bring in higher signal-to-noise ratio. In addition,Figure 4 demonstrates a clear decrease of the quality of communication from 20 to 60 MHz. As the transmission of 50 MHz is almost the same as the one of 40 MHz,it is not shown in the figure to increase the contrast ratio. Actually the signal-to-noise ratio is so bad that the received signal can barely be recognized at 60 MHz. This can be attributed to the high frequency loss of the signal transmission line. Limited by the transmission line bandwidth,the signal drops while the noise level is nearly the same. A frequency characteristic measurement shows that the 3 dB bandwidth of the laser is about 800 MHz,and the detector has a response time shorter than 1 ns. Therefore high performance communication system with higher signal-to-noise ratio and bandwidth can be obtained with high frequency transmission components.

Figure Fig4. Frequency characteristics of the transmitting system. The lines 1 are input sinusoidal signals and the lines 2 are received ones. The transmission of (a) 20 MHz,(b) 30 MHz,(c) 40 MHz,and (d) 60 MHz sinusoidal signal.

DownLoad: Full-Size Img PowerPoint

For further experiment,a video signal was transmitted through the link,as shown in Figure 5. The target of the camera is an oscilloscope displaying a sinusoidal signal. The video signal from the camera is amplitude modulated with a 30 MHz carrier wave. The amplitude of the modulated signal was 100 mV and the modulation depth was 100%. Then the received video signal from the detector was amplified by an LNA and demodulated. After that,the video signal was displayed with an LCD screen to test the communication quality visually. As shown in the picture,the image displayed by the LCD screen is distinct. There is no distortion or false color. The clarity of the image is limited by the quality of the camera. That is to say,a free-space video transmission system has been constructed successfully,though the bandwidth is not so attractive.

Figure Fig5. Picture of the video transmission. An oscilloscope displaying sinusoidal wave was chosen as the target of the analog camera. The transmission result was displayed by an LCD.

DownLoad: Full-Size Img PowerPoint

The transmitted results acquired by our link system provide a proof-of-concept demonstration,however the signal-to-noise ratio and bandwidth should be improved in further work. For this system,the signal-to-noise ratio should be improved from two aspects. For one thing,a detector with a higher responsivity and better optical collimation system will increase the received signal. For another,low-pass filters to eliminate the high frequency noise will be helpful. The bandwidth of the system represents the overall frequency characteristics of the communication link,including the laser,the detector,the circuits,and the signal transmission lines. It is mainly restricted by the circuits and the signal transmission lines. A high performance communication system can be obtained with high frequency circuits and transmission lines. Although the potential wide bandwidth of the QCL was not realized in this link,it should be mentioned that neither the packaging nor the processing of the devices were optimized for high frequency operation.

4. Conclusion

A free-space infrared analogue communication link setup using a QCL as the source and an HgCdTe detector as the receiver is constructed and used to demonstrate the potential of QCLs for space optical communication. The laser is a continuous-wave room-temperature operation of distributed feedback device emitting at 4.7 $\mu$ m. The HgCdTe detector works at room temperature with peak response wavelength of about 5 $\mu$ m. Sinusoidal signals at a highest frequency of 40 MHz and modulated video signals with a carrier frequency of 30 MHz were successfully transmitted with this experimental setup. Our research has provided a proof-of-concept demonstration of space optical communication application with QCLs. The highest operating frequency of our setup was determined by the limited bandwidth of circuits and communication line. A high performance communication system can be obtained with high frequency circuit components. In addition,the collimating beam expanding system would be achieved for practical long-distance communication.

References

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]

Fig1. Power-current-voltage curve of the QCL. The picture on the upper left corner is the laser employed in the experiment.

DownLoad: Full-Size Img PowerPoint

Fig2. Normalized spectra of the laser emission and the detector response.

DownLoad: Full-Size Img PowerPoint

Fig3. Scheme of FSO communication system.

DownLoad: Full-Size Img PowerPoint

Fig4. Frequency characteristics of the transmitting system. The lines 1 are input sinusoidal signals and the lines 2 are received ones. The transmission of (a) 20 MHz,(b) 30 MHz,(c) 40 MHz,and (d) 60 MHz sinusoidal signal.

DownLoad: Full-Size Img PowerPoint

Fig5. Picture of the video transmission. An oscilloscope displaying sinusoidal wave was chosen as the target of the analog camera. The transmission result was displayed by an LCD.

DownLoad: Full-Size Img PowerPoint

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]

1	Experimental study on phase noise of terahertz quantum cascade laser frequency comb and dual-comb sources Lulu Zheng, Xianglong Bi, Xuhong Ma, Guibin Liu, Binbin Liu, et al. Journal of Semiconductors, 2024, 45(12): 122401. doi: 10.1088/1674-4926/24060028
2	High power λ ~ 8.5 μm quantum cascade laser grown by MOCVD operating continuous-wave up to 408 K Teng Fei, Shenqiang Zhai, Jinchuan Zhang, Ning Zhuo, Junqi Liu, et al. Journal of Semiconductors, 2021, 42(11): 112301. doi: 10.1088/1674-4926/42/11/112301
3	Improved efficiency and photo-stability of methylamine-free perovskite solar cells via cadmium doping Yong Chen, Yang Zhao, Qiufeng Ye, Zema Chu, Zhigang Yin, et al. Journal of Semiconductors, 2019, 40(12): 122201. doi: 10.1088/1674-4926/40/12/122201
4	Room temperature continuous wave operation of quantum cascade laser at λ ~ 9.4 μm Chuncai Hou, Yue Zhao, Jinchuan Zhang, Shenqiang Zhai, Ning Zhuo, et al. Journal of Semiconductors, 2018, 39(3): 034001. doi: 10.1088/1674-4926/39/3/034001
5	Broad area quantum cascade lasers operating in pulsed mode above 100 ℃ at λ~4.7μm Yue Zhao, Fangliang Yan, Jinchuan Zhang, Fengqi Liu, Ning Zhuo, et al. Journal of Semiconductors, 2017, 38(7): 074005. doi: 10.1088/1674-4926/38/7/074005
6	A monolithic integrated low-voltage deep brain stimulator with wireless power and data transmission Zhang Zhang, Ye Tan, Jianmin Zeng, Xu Han, Xin Cheng, et al. Journal of Semiconductors, 2016, 37(9): 095003. doi: 10.1088/1674-4926/37/9/095003
7	Distributed feedback quantum cascade lasers operating in continuous-wave mode at λ ≈ 7.6 μm Zhang Jinchuan, Wang Lijun, Liu Wanfeng, Liu Fengqi, Zhao Lihua, et al. Journal of Semiconductors, 2012, 33(2): 024005. doi: 10.1088/1674-4926/33/2/024005
8	Porous waveguide facilitated low divergence quantum cascade laser Yin Wen, Lu Quanyong, Liu Wanfeng, Zhang Jinchuan, Wang Lijun, et al. Journal of Semiconductors, 2011, 32(6): 064008. doi: 10.1088/1674-4926/32/6/064008
9	Holographic fabricated continuous wave operation of distributed feedback quantum cascade lasers at λ ≈ 8.5 μm Zhang Jinchuan, Wang Lijun, Zhang Wei, Liu Wanfeng, Liu Junqi, et al. Journal of Semiconductors, 2011, 32(4): 044008. doi: 10.1088/1674-4926/32/4/044008
10	Optical bistability in a two-section InAs quantum-dot laser Jiang Liwen, Ye Xiaoling, Zhou Xiaolong, Jin Peng, Lü Xueqin, et al. Journal of Semiconductors, 2010, 31(11): 114012. doi: 10.1088/1674-4926/31/11/114012
11	Analysis of surface emitting distributed-feedback quantum cascade laser based on a surface-plasmon waveguide Guo Wanhong, Lu Quanyong, Liu Junqi, Zhang Wei, Jiang Yuchao, et al. Journal of Semiconductors, 2010, 31(11): 114014. doi: 10.1088/1674-4926/31/11/114014
12	Waveguide Simulation of a THz Si/SiGe Quantum Cascade Laser Chen Rui, Lin Guijiang, Chen Songyan, Li Cheng, Lai Hongkai, et al. Journal of Semiconductors, 2008, 29(5): 893-897.
13	One-Dimensional InP-Based Photonic Crystal Quantum Cascade Laser Emitting at 5.36μm Li Lu, Shao Ye, Liu Junqi, Liu Fengqi, Wang Zhanguo, et al. Journal of Semiconductors, 2008, 29(7): 1278-1280.
14	Waveguide Optimization for a 9.0μm GaAs-Based Quantum Cascade Laser Li Lu, Liu Fengqi, Shao Ye, Liu Junqi, Wang Zhanguo, et al. Chinese Journal of Semiconductors , 2007, 28(1): 31-35.
15	Self-Pulsation Dynamics in GaAs/AIGaAs Quantum Cascade Lasers Liu Junqi, Liu Fengqi, Li Lu, Shao Ye, Guo Yu, et al. Chinese Journal of Semiconductors , 2007, 28(S1): 44-47.
16	Study of NiSi/Si Interface by Cross-Section Transmission Electron Microscopy Jiang Yulong, Ru Guoping, Qu Xinping, Li Bingzong Chinese Journal of Semiconductors , 2006, 27(2): 223-228.
17	Energy Band Design for a Terahertz Si/SiGe Quantum Cascade Laser Lin Guijiang, Lai Hongkai, Li Cheng, Chen Songyan, Yu Jinzhong, et al. Chinese Journal of Semiconductors , 2006, 27(5): 916-920.
18	Monte Carlo Simulation of Impurity Scattering Effect in Resonant-Phonon-Assisted Terahertz Quantum-Cascade Lasers Cao Juncheng, Lü Jingtao Chinese Journal of Semiconductors , 2006, 27(2): 304-308.
19	Single Mode Operation of Short-Cavity Quantum Cascade Lasers Liu Fengqi, Guo Yu, Li Lu, Shao Ye, Liu Junqi, et al. Chinese Journal of Semiconductors , 2006, 27(4): 679-682.
20	Room Temperature Operation of Strain-Compensated 5.5μm Quantum Cascade Lasers Lu Xiuzhen, Liu Fengqi, Liu Junqi, Jin Peng, Wang Zhanguo, et al. Chinese Journal of Semiconductors , 2005, 26(12): 2267-2270.

1.	Du, S.-H., Zheng, X.-T., Jia, H. et al. Structural design of a wide-ridge mid-wave infrared quantum cascade laser based on a supersymmetric waveguide \| [基于超对称波导的宽脊中波量子级联激光器结构设计]. Hongwai Yu Haomibo Xuebao/Journal of Infrared and Millimeter Waves, 2025, 44(3): 447-453. doi:10.11972/j.issn.1001-9014.2025.03.015
2.	Dąbrowski, K., Gawron, W., Kubiszyn, Wu, Y.-R. et al. Response time of the type-II superlattice InAs/InAsSb mid-infrared interband cascade photodetector for HOT conditions. Optics and Laser Technology, 2025. doi:10.1016/j.optlastec.2024.112172
3.	Yao, J.-L., Zhang, J.-C., Cheng, F.-M. et al. 1 × 2 MMI teardrop quantum cascade lasers with a high SMSR up to 45 dB. Infrared Physics and Technology, 2025. doi:10.1016/j.infrared.2025.105731
4.	Grillot, F., Poletti, T., Pes, S. Progress in mid-infrared optoelectronics for high-speed free-space data throughput. APL Photonics, 2025, 10(1): 010905. doi:10.1063/5.0230260
5.	Joharifar, M., Dely, H., Durupt, L. et al. Exploring Mid-IR FSO Communications With Unipolar Quantum Optoelectronics. Journal of Lightwave Technology, 2025, 43(4): 1633-1643. doi:10.1109/JLT.2024.3472452
6.	Zhang, M., Wang, X., Yang, S. et al. High-Efficiency Fiber Combining of Long-Wave Infrared Quantum Cascade Lasers \| [长波红外量子级联激光器的高效率光纤合束]. Guangxue Xuebao/Acta Optica Sinica, 2024, 44(8): 0814003. doi:10.3788/AOS231973
7.	Shen, Z., Yao, J., Huang, J. et al. High-Speed Mid-Wave Infrared Uni-Traveling Carrier Photodetector With Inductive Peaked Dewar Packaging. Journal of Lightwave Technology, 2024, 42(5): 1504-1510. doi:10.1109/JLT.2023.3322967
8.	Zhang, S., Zhu, L., Li, M. et al. Phase-locked taper array for mid-infrared quantum cascade lasers with Talbot cavities. Proceedings of SPIE - The International Society for Optical Engineering, 2024. doi:10.1117/12.3032520
9.	Su, Y., Tian, W., Yu, Y. et al. Free-space transmission of picosecond-level, high-speed optical pulse streams in the 3 µm band. Optics Express, 2023, 31(17): 27433-27449. doi:10.1364/OE.497175
10.	Li, Y., Gan, T., Bai, B. et al. Optical information transfer through random unknown diffusers using electronic encoding and diffractive decoding. Advanced Photonics, 2023, 5(4): 046009. doi:10.1117/1.AP.5.4.046009
11.	Su, Y., Meng, J., Wei, T. et al. 150 Gbps multi-wavelength FSO transmission with 25-GHz ITU-T grid in the mid-infrared region. Optics Express, 2023, 31(9): 15156-15169. doi:10.1364/OE.487668
12.	Shen, Z., Yao, J., Lu, H. et al. Mid-Wave Infrared High-Speed InAs/GaSb Superlattice Uni-Traveling Carrier Photodetector. 2023. doi:10.1109/OECC56963.2023.10209925
13.	Guan, Y., Sun, R., Zhuo, N. et al. Room temperature continuous-wave operation of a dual-wavelength quantum cascade laser. Chinese Optics Letters, 2023, 21(1): 011408. doi:10.3788/COL202321.011408
14.	Sinhal, M., Johnson, A., Willitsch, S. Frequency stabilisation and SI tracing of mid-infrared quantum-cascade lasers for precision molecular spectroscopy. Molecular Physics, 2023, 121(17-18): e2144519. doi:10.1080/00268976.2022.2144519
15.	Seminara, M., Gabbrielli, T., Corrias, N. et al. Characterization of noise regimes in mid-IR free-space optical communication based on quantum cascade lasers. Optics Express, 2022, 30(25): 44640-44656. doi:10.1364/OE.470031
16.	Sang, M.-S., Xu, G.-Q., Qiao, H. et al. High speed uncooled MWIR infrared HgCdTe photodetector based on graded bandgap structure \| [基于梯度能带结构的高速非制冷中波红外 HgCdTe 探测器]. Hongwai Yu Haomibo Xuebao/Journal of Infrared and Millimeter Waves, 2022, 41(6): 972-979. doi:10.11972/j.issn.1001-9014.2022.06.005
17.	Basiri, A., Rafique, M.Z.E., Bai, J. et al. Ultrafast low-pump fluence all-optical modulation based on graphene-metal hybrid metasurfaces. Light: Science and Applications, 2022, 11(1): 102. doi:10.1038/s41377-022-00787-8
18.	Jia, Z.-W., Li, L., Guo, Y.-Y. et al. Periodic and chaotic oscillations in mutual-coupled mid-infrared quantum cascade lasers. Chinese Physics B, 2022, 31(10): 100505. doi:10.1088/1674-1056/ac8f34
19.	Didier, P., Dely, H., Bonazzi, T. et al. High-capacity free-space optical link in the midinfrared thermal atmospheric windows using unipolar quantum devices. Advanced Photonics, 2022, 4(5): 056004. doi:10.1117/1.AP.4.5.056004
20.	Chen, B.. Equivalent Circuit Model of the RF Characteristics of Multi-Stage Infrared Photodetectors. Journal of Lightwave Technology, 2022, 40(15): 5224-5230. doi:10.1109/JLT.2022.3171812
21.	Pang, X., Ozolins, O., Jia, S. et al. Bridging the Terahertz Gap: Photonics-Assisted Free-Space Communications From the Submillimeter-Wave to the Mid-Infrared. Journal of Lightwave Technology, 2022, 40(10): 3149-3162. doi:10.1109/JLT.2022.3153139
22.	Huang, J., Shen, Z., Wang, Z. et al. High-Speed Mid-Wave Infrared Uni-Traveling Carrier Photodetector Based on InAs/InAsSb Type-II Superlattice. IEEE Electron Device Letters, 2022, 43(5): 745-748. doi:10.1109/LED.2022.3163660
23.	Cherotchenko, E.D., Dudelev, V.V., Mikhailov, D.A. et al. Observation of Long Turn-On Delay in Pulsed Quantum Cascade Lasers. Journal of Lightwave Technology, 2022, 40(7): 2104-2110. doi:10.1109/JLT.2021.3134837
24.	Xiao, Y., Zhou, L., Pan, Z. et al. Physically-secured high-fidelity free-space optical data transmission through scattering media using dynamic scaling factors. Optics Express, 2022, 30(5): 8186-8198. doi:10.1364/OE.448943
25.	Dai, Z., Huang, J., Chen, B. MWIR InAs/InAsSb type-II Superlattice Photodetector for High-Speed Operation. 2022. doi:10.1109/IPC53466.2022.9975627
26.	Spitz, O., Didier, P., Durupt, L. et al. Free-Space Communication with Directly Modulated Mid-Infrared Quantum Cascade Devices. IEEE Journal of Selected Topics in Quantum Electronics, 2022, 28(1): 9483581. doi:10.1109/JSTQE.2021.3096316
27.	Kumar, M., Prasad, S. The properties of mid infrared surface modes at the interface of air and one dimensional ternary photonic crystal. Materials Today Communications, 2021. doi:10.1016/j.mtcomm.2021.102889
28.	Pirotta, S., Tran, N.-L., Jollivet, A. et al. Fast amplitude modulation up to 1.5 GHz of mid-IR free-space beams at room-temperature. Nature Communications, 2021, 12(1): 799. doi:10.1038/s41467-020-20710-2
29.	Mikołajczyk, J., Weih, R., Motyka, M. Optical wireless link operated at the wavelength of 4.0 µm with commercially available interband cascade laser. Sensors, 2021, 21(12): 4102. doi:10.3390/s21124102
30.	Mikołajczyk, J.. A comparison study of data link with medium-wavelength infrared pulsed and cw quantum cascade lasers. Photonics, 2021, 8(6): 203. doi:10.3390/photonics8060203
31.	Mikołajczyk, J.. Data link with a high-power pulsed quantum cascade laser operating at the wavelength of 4.5 µm. Sensors, 2021, 21(9): 3231. doi:10.3390/s21093231
32.	Hai, Y., Zou, Y., Ma, X. et al. Narrow-linewidth surface-emitting distributed feedback semiconductor lasers with low threshold current. Optics and Laser Technology, 2021. doi:10.1016/j.optlastec.2020.106631
33.	Pang, X., Ozolins, O., Zhang, L. et al. Free-Space Communications Enabled by Quantum Cascade Lasers. Physica Status Solidi (A) Applications and Materials Science, 2021, 218(3): 2000407. doi:10.1002/pssa.202000407
34.	Guan, Y.-J., Liu, F.-Q., Wang, Z.-G. et al. High Powered Tapered Sampling Grating Distributed Feedback Quantum Cascade Lasers. IEEE Photonics Technology Letters, 2020, 32(6): 305-308. doi:10.1109/LPT.2020.2973089
35.	Chen, Y., Chai, X., Xie, Z. et al. High-Speed Mid-Infrared Interband Cascade Photodetector Based on InAs/GaAsSb Type-II Superlattice. Journal of Lightwave Technology, 2020, 38(4): 939-945. doi:10.1109/JLT.2019.2950607
36.	Hamza, A.S., Deogun, J.S., Alexander, D.R. Classification Framework for Free Space Optical Communication Links and Systems. IEEE Communications Surveys and Tutorials, 2019, 21(2): 1346-1382. doi:10.1109/COMST.2018.2876805
37.	Zhao, Y., Zhang, J., Liu, C. et al. Progress in mid-and far-infrared quantum cascade laser(invited) \| [中远红外量子级联激光器研究进展(特邀)]. Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering, 2018, 47(10): 1003001. doi:10.3788/IRLA201847.1003001
38.	Zhao, Y., Zhang, J.-C., Zhuo, N. et al. Low voltage-defect quantum cascade lasers based on excited-states injection at λ ∼ 8.5 μm. Applied Optics, 2018, 57(26): 7579-7583. doi:10.1364/AO.57.007579
39.	Jia, X.-F., Wang, L.-J., Zhuo, N. et al. Multi-wavelength sampled bragg grating quantum cascade laser arrays. Photonics Research, 2018, 6(7): 721-725. doi:10.1364/PRJ.6.000721
40.	Huang, Q., Liu, D., Chen, Y. et al. Secure free-space optical communication system based on data fragmentation multipath transmission technology. Optics Express, 2018, 26(10): 13536-13542. doi:10.1364/OE.26.013536
41.	Hou, C., Zhao, Y., Zhang, J. et al. Room temperature continuous wave operation of quantum cascade laser at λ ∼ 9.4 μm. Journal of Semiconductors, 2018, 39(3): 034001. doi:10.1088/1674-4926/39/3/034001
42.	Jia, X., Wang, L., Jia, Z. et al. Fast Swept-Wavelength, Low Threshold-Current, Continuous-Wave External Cavity Quantum Cascade Laser. Nanoscale Research Letters, 2018. doi:10.1186/s11671-018-2765-1
43.	Zhao, Y., Zhang, J.-C., Cheng, F.-M. et al. Tapered Quantum Cascade Laser Arrays Integrated with Talbot Cavities. Nanoscale Research Letters, 2018. doi:10.1186/s11671-018-2617-z
44.	Wang, D.-B., Zhang, J.-C., Cheng, F.-M. et al. Stable Single-Mode Operation of Distributed Feedback Quantum Cascade Laser by Optimized Reflectivity Facet Coatings. Nanoscale Research Letters, 2018. doi:10.1186/s11671-018-2455-z
45.	Jia, Z.-W., Wang, L.-J., Zhang, J.-C. et al. High Efficiency, Low Power-Consumption DFB Quantum Cascade Lasers Without Lateral Regrowth. Nanoscale Research Letters, 2017, 12(1): 281. doi:10.1186/s11671-017-2064-2
46.	Jia, X., Wang, L., Zhuo, N. et al. Single-Mode Quantum Cascade Laser at 5.1 μm with Slotted Refractive Index Modulation. IEEE Photonics Technology Letters, 2017, 29(22): 1959-1962. doi:10.1109/LPT.2017.2757935
47.	Wang, F., Zhuo, N., Liu, S. et al. Quantum dot quantum cascade photodetector using a laser structure. Chinese Optics Letters, 2017, 15(10): 102301. doi:10.3788/COL201715.102301
48.	Liu, D., Wang, Z., Liu, J. et al. Performance analysis of 1-km free-space optical communication system over real atmospheric turbulence channels. Optical Engineering, 2017, 56(10): 106111. doi:10.1117/1.OE.56.10.106111
49.	Zhao, Y., Zhang, J.-C., Zhou, Y.-H. et al. External-cavity beam combining of 4-channel quantum cascade lasers. Infrared Physics and Technology, 2017. doi:10.1016/j.infrared.2017.05.012
50.	Jia, Z., Wang, L., Tan, S. et al. Improvement of Buried Grating DFB Quantum Cascade Lasers by Small-Angle Tapered Structure. IEEE Photonics Technology Letters, 2017, 29(10): 783-785. doi:10.1109/LPT.2017.2681127
51.	Kang, G., Xu, Z., Wang, J. et al. Long-wave infrared wireless laser communication performance under atmospheric turbulence conditions. Laser and Optoelectronics Progress, 2017, 54(3): 030603. doi:10.3788/LOP54.030603
52.	Jia, Z., Wang, L., Zhang, J. et al. Stable single-mode distributed feedback quantum cascade lasers at λ ∼ 4.25 μm with low power consumption. Solid-State Electronics, 2016. doi:10.1016/j.sse.2016.07.028
53.	Liu, Y.-H., Zhang, J.-C., Yan, F.-L. et al. High efficiency, single-lobe surface-emitting DFB/DBR quantum cascade lasers. Optics Express, 2016, 24(17): 19545-19551. doi:10.1364/OE.24.019545
54.	Li, Y.-Y., Liu, J.-Q., Liu, F.-Q. et al. High power-efficiency terahertz quantum cascade laser. Chinese Physics B, 2016, 25(8): 084206. doi:10.1088/1674-1056/25/8/084206

Search

GET CITATION

Chuanwei Liu, Shenqiang Zhai, Jinchuan Zhang, Yuhong Zhou, Zhiwei Jia, Fengqi Liu, Zhanguo Wang. Free-space communication based on quantum cascade laser[J]. Journal of Semiconductors, 2015, 36(9): 094009. doi: 10.1088/1674-4926/36/9/094009

C W Liu, S Q Zhai, J C Zhang, Y H Zhou, Z W Jia, F Q Liu, Z G Wang. Free-space communication based on quantum cascade laser[J]. J. Semicond., 2015, 36(9): 094009. doi: 10.1088/1674-4926/36/9/094009.

Export: BibTex EndNote

Article Metrics

Article views: 3132 Times PDF downloads: 62 Times Cited by: 54 Times

History

Received: 16 April 2015 Revised: Online: Published: 01 September 2015

Article Navigation > Journal of Semiconductors > 2015 > 36(9): 094009

Chuanwei Liu, Shenqiang Zhai, Jinchuan Zhang, Yuhong Zhou, Zhiwei Jia, Fengqi Liu, Zhanguo Wang. Free-space communication based on quantum cascade laser[J]. Journal of Semiconductors, 2015, 36(9): 094009. doi: 10.1088/1674-4926/36/9/094009 ****C W Liu, S Q Zhai, J C Zhang, Y H Zhou, Z W Jia, F Q Liu, Z G Wang. Free-space communication based on quantum cascade laser[J]. J. Semicond., 2015, 36(9): 094009. doi: 10.1088/1674-4926/36/9/094009.

Citation:

PDF( 178 KB)

Free-space communication based on quantum cascade laser

DOI: 10.1088/1674-4926/36/9/094009

Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China

Funds:

Project supported by the State Key Development Program for Basic Research of China (Nos. 2013CB632801, 2013CB632803) and the National Natural Science Foundation of China (Nos. 61435014, 61306058, 61274094).

More Information

Corresponding author: Zhai Shenqiang, zsqlzsmbj@semi.ac.cn
Received Date: 2015-04-16
Accepted Date: 2015-05-07
Published Date: 2015-01-25

Abstract

Abstract

A free-space communication based on a mid-infrared quantum cascade laser (QCL) is presented. A room-temperature continuous-wave distributed-feedback (DFB) QCL combined with a mid-infrared detector comprise the basic unit of the communication system. Sinusoidal signals at a highest frequency of 40 MHz and modulated video signals with a carrier frequency of 30 MHz were successfully transmitted with this experimental setup. Our research has provided a proof-of-concept demonstration of space optical communication application with QCL. The highest operation frequency of our setup was determined by the circuit-limited modulation bandwidth. A high performance communication system can be obtained with improved modulation circuit system.
- quantum cascade laser,
- free-space communication,
- video transmission

FullText(HTML)

1. Introduction

Free-space optical (FSO) systems are promising networking solutions for broadband communication technologies due to their clear advantages,such as unlimited bandwidth (no RF spectrum licensing),low cost,high security and mobility^{[1, 2, 3, 4]}. As the most optimum light source in the infrared wavelength range,quantum cascade lasers (QCLs) present a huge potential for the application in this field^{[5, 6, 7]}. For one thing,their emission wavelengths are typically in the so-called atmospheric window regions,i.e.,3-5 $\mu$ m and 8-14 $\mu$ m. Thus the radiation suffers less attenuation than shorter wavelength light from near-infrared (NI) lasers,which permits rather longer propagation distance even in adverse weather conditions^[8]. For another,the fast internal lifetimes of these devices allow for high operating and modulation frequency of up to 5-10 GHz^[5],which promise very high communication bandwidth. In addition,FSO based on mid-IR QCLs is far more secure because of technological barriers to the high performance infrared detectors,making laser beams harder to detect and even harder to intercept and crack. Therefore the applications of QCLs for FSO have attracted more and more research and commercial interests^{[10, 11, 12]},especially as the QCL technology has become gradually mature in recent years. The continuous-wave room-temperature high-speed devices have paved the way for the wide use of QCL in FSO area.

In this paper,a free-space mid-infrared communication setup based on a home-made QCL in our research group is constructed to provide a proof-of-concept demonstration of space optical communication application with QCL. The laser is a room-temperature continuous-wave operation of DFB device emitting at 4.7 $\mu$ m. A HgCdTe detector operating at room temperature with peak response wavelength of about 5 $\mu$ m is used to receive light. Sinusoidal signals at a highest frequency of 40 MHz and modulated video signals with a carrier frequency of 30 MHz were successfully transmitted with this experimental setup. The highest operation frequency of our setup was determined by the circuit-limited modulation bandwidth. A high performance communication system can be obtained with improved modulation circuit and optical optimization system.

2. FSO communication system

2.1 Laser and detector

The laser used in this experiment was grown by molecular beam epitaxy (MBE) in the InGaAs/InAlAs material system. The active region is designed based on the so-called double-resonant-phonon. The laser chip,consisting of 2-mm-long,10- $\mu$ m-wide deep etched ridge is epilayer-down bonded to a copper heat sink. The laser was packaged in a HHL (high heat load) and collimated by an optic lens inside the package,as illustrated in the inset of . The device can operate in room-temperature continuous-wave (CW) mode emitting around 4.7 $\mu$ m. Figure 1 shows the photoelectric properties of the device. The threshold current of the QCL is about 300 mA. In the experiment,DC-bias current was set at about 350 mA with about 12 mW output power.

Figure Fig1. Power-current-voltage curve of the QCL. The picture on the upper left corner is the laser employed in the experiment.

DownLoad: Full-Size Img PowerPoint

The HgCdTe detector in our setup is bought from VIGO (PVMI-10.6) and has a peak response at about 5 $\mu$ m. It has a response time shorter than 1 ns,which can satisfy the frequency requirement in our experiment. However,the detector operated under photovoltaic mode,which limited the responsivity and requires higher light power in the experiment. Normalized spectra of the laser emission and the detector response are demonstrated in Figure 2. It is clear that the detector can easily detect the emission light of the laser.

Figure Fig2. Normalized spectra of the laser emission and the detector response.

DownLoad: Full-Size Img PowerPoint

2.2 Experimental technique

A schematic of the experimental setup is shown in . The input signals to be transmitted,i.e.,sinusoidal signals and modulated video signal,and DC current are synthesized to drive the laser through a bias-T. The sinusoidal signals are provided by a function generator,while the modulated video signal is from a camera and modulated by a home-made modulator. Being well packaged,it is not necessary to collimate the emitted radiation from the device again. Using two plane mirrors,the radiation is guided along a 2.5 m optical path in the air,and then focused onto the detector with a CaF $_{2}$ optical lens. The 2.5 m range is limited by the length of the optical table where the emitter and receiver are fixed. However in the practical application for long-distance transmission,the laser beam needs to be perfectly collimated with a collimating beam expanding system. The electrical signal from the detector was amplified by a low-noise-amplifier (LNA) and then added to a home-made demodulator. After demodulation,the transmitted signals can be examined with an oscilloscope. In addition,the video signal can be displayed with an LCD screen to test the communication quality visually.

Figure Fig3. Scheme of FSO communication system.

DownLoad: Full-Size Img PowerPoint

3. Results and discussions

Sinusoidal signals with different frequencies generated by the signal generator were transmitted through the link. The time traces of the input signals and received signals are shown in Figure 4. The received signals show a clear phase shift compared with input ones,which is caused by the amplifier circuits and the response time of the detector. At 20 MHz,the waveform of the received signal is in good accordance with the input signal. However the signal-to-noise ratio is not so good,which can be attributed to the low responsivity of the photovoltaic detector and high noise from the circuits. A detector with higher responsivity and a high-pass filter to eliminate the low frequency noise will bring in higher signal-to-noise ratio. In addition,Figure 4 demonstrates a clear decrease of the quality of communication from 20 to 60 MHz. As the transmission of 50 MHz is almost the same as the one of 40 MHz,it is not shown in the figure to increase the contrast ratio. Actually the signal-to-noise ratio is so bad that the received signal can barely be recognized at 60 MHz. This can be attributed to the high frequency loss of the signal transmission line. Limited by the transmission line bandwidth,the signal drops while the noise level is nearly the same. A frequency characteristic measurement shows that the 3 dB bandwidth of the laser is about 800 MHz,and the detector has a response time shorter than 1 ns. Therefore high performance communication system with higher signal-to-noise ratio and bandwidth can be obtained with high frequency transmission components.

Figure Fig4. Frequency characteristics of the transmitting system. The lines 1 are input sinusoidal signals and the lines 2 are received ones. The transmission of (a) 20 MHz,(b) 30 MHz,(c) 40 MHz,and (d) 60 MHz sinusoidal signal.

DownLoad: Full-Size Img PowerPoint

For further experiment,a video signal was transmitted through the link,as shown in Figure 5. The target of the camera is an oscilloscope displaying a sinusoidal signal. The video signal from the camera is amplitude modulated with a 30 MHz carrier wave. The amplitude of the modulated signal was 100 mV and the modulation depth was 100%. Then the received video signal from the detector was amplified by an LNA and demodulated. After that,the video signal was displayed with an LCD screen to test the communication quality visually. As shown in the picture,the image displayed by the LCD screen is distinct. There is no distortion or false color. The clarity of the image is limited by the quality of the camera. That is to say,a free-space video transmission system has been constructed successfully,though the bandwidth is not so attractive.

Figure Fig5. Picture of the video transmission. An oscilloscope displaying sinusoidal wave was chosen as the target of the analog camera. The transmission result was displayed by an LCD.

DownLoad: Full-Size Img PowerPoint

The transmitted results acquired by our link system provide a proof-of-concept demonstration,however the signal-to-noise ratio and bandwidth should be improved in further work. For this system,the signal-to-noise ratio should be improved from two aspects. For one thing,a detector with a higher responsivity and better optical collimation system will increase the received signal. For another,low-pass filters to eliminate the high frequency noise will be helpful. The bandwidth of the system represents the overall frequency characteristics of the communication link,including the laser,the detector,the circuits,and the signal transmission lines. It is mainly restricted by the circuits and the signal transmission lines. A high performance communication system can be obtained with high frequency circuits and transmission lines. Although the potential wide bandwidth of the QCL was not realized in this link,it should be mentioned that neither the packaging nor the processing of the devices were optimized for high frequency operation.

4. Conclusion

A free-space infrared analogue communication link setup using a QCL as the source and an HgCdTe detector as the receiver is constructed and used to demonstrate the potential of QCLs for space optical communication. The laser is a continuous-wave room-temperature operation of distributed feedback device emitting at 4.7 $\mu$ m. The HgCdTe detector works at room temperature with peak response wavelength of about 5 $\mu$ m. Sinusoidal signals at a highest frequency of 40 MHz and modulated video signals with a carrier frequency of 30 MHz were successfully transmitted with this experimental setup. Our research has provided a proof-of-concept demonstration of space optical communication application with QCLs. The highest operating frequency of our setup was determined by the limited bandwidth of circuits and communication line. A high performance communication system can be obtained with high frequency circuit components. In addition,the collimating beam expanding system would be achieved for practical long-distance communication.

References(11)

References

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]