-
中红外光电器件在传感与成像等领域具有重要且广泛的应用,目前相关的光学系统往往由分立的器件组成,将这些体积庞大的光学系统集成到一块芯片上是光子集成研究的长期目标,近些年,国内外许多研究团队报道了中红外片上传感和片上成像方面的研究成果,但是这些研究基本都通过将外置光源的输出耦合进入芯片来实现片上功能,激光光源实际上并没有在片上集成,实现激光器的光子集成是实现真正的片上传感和片上成像的重要一步。另外一方面,光子集成平台可以提供低损耗的光波导、宽调谐的滤波器、高品质因子的微环谐振器,将III-V族半导体激光器与这些元件集成到一起可以实现传统中红外半导体激光平台难以实现的宽调谐、窄线宽等先进功能。文中详细介绍了近些年中红外QCL光子集成的研究进展,表1展示了不同光子集成方式之间的对比。目前片上集成的QCL在性能方面与传统III-V衬底上的器件还有较大差距,这一方面是因为异质集成增加了器件的工艺难度,同时QCL与无源波导之间的较差的耦合效率也使得器件的性能不如预期,此外片上集成也增加了QCL器件的散热难度。在后续的研究中,需要优化QCL与无源波导的耦合结构,研究实现QCL高效片上散热的方法,探索硅上外延生长的新途径,实现QCL与光子芯片的晶圆集成,使完全集成的中红外光子传感器成为现实。
表 1 中红外QCL不同光子集成方式的对比
Table 1. Comparison of different photonic integration approaches for mid-infrared QCLs
Integration
approachIntegration
densityActive-passive
couplingHeat dissipation Process yield Current
performanceDetector
integrationMonolithic integration on InP ★★★ ★★★ ★★★ ★★★ ★★ ★★ Monolithic integration on Silicon ★★★ − ★★ ★ ★ ★★ Heterogeneous integration on silicon ★★★ ★★ ★★ ★★ ★ ★ Hybrid external cavity ★ ★ ★★★ ★★★ ★ −
Photonics integration of mid-infrared quantum cascade laser (Invited)
-
摘要: 中红外光子集成芯片在环保监测、医疗诊断和国防安全等领域具有广泛的应用前景,但激光光源与无源波导光路的片上集成仍是中红外集成光学需要攻克的关键难题之一。量子级联激光器(QCL)是中红外波段的重要半导体激光光源,文中介绍了近几年中红外QCL在光子集成方面的研究进展,包括InP基单片集成、硅基单片集成、硅基异质键合集成和III-V/锗混合外腔激光器。Abstract: Mid-infrared photonic integrated circuits have been attracting a lot of interest for applications in environmental monitoring, medical diagnosis and national defense. However, the integration of laser sources with low-loss mid-infrared waveguide circuits is challenging. Quantum cascade lasers (QCLs) are important semiconductor laser sources operating in the mid-infrared spectral range. In this review paper, the research progress of the photonics integration of mid-infrared QCLs in recent years was introduced. Several different approaches were reviewed, including monolithic integration on InP, monolithic integration on silicon, heterogeneous integration on silicon and III-V/Germanium hybrid external cavity laser.
-
Key words:
- quantum cascade laser /
- photonics integration /
- mid-infrared /
- silicon photonics /
- optical sensing
-
图 1 (a) MIT林肯实验室研制的单片集成QCL器件的结构示意图,QCL波导的其中一截被选择性地注入质子以减少自由载流子与子带跃迁损耗[12];(b)倏逝波耦合的单片集成QCL器件的结构示意图[13];(c)通过对接耦合实现中红外QCL与低损耗无源波导的单片集成,在湿法蚀刻移除掉大部分区域的有源层后,InGaAs无源波导层通过MOVPE生长在QCL晶圆上[14];(d)图1(c)所示单片集成QCL器件在CW模式下的光功率-电流-电压关系(LIV)曲线[14]
Figure 1. (a) Monolithically integrated QCL device developed by MIT Lincoln Laboratory, part of the QCL waveguide is proton implanted to reduce the free-carrier and intersubband transition loss[12]; (b) Schematic of the evanescently coupled monolithically integrated QCL device[13]; (c) Monolithic integration of mid-infrared QCL with low-loss passive waveguides via butt-coupling[14], the InGaAs passive waveguide layer is grown on the sample after most area of the wafer is removed by wet etching;(d) CW mode light-current-voltage (LIV) curve of the monolithically integrated QCL device schematically shown in Fig.1(c) [14]
表 1 中红外QCL不同光子集成方式的对比
Table 1. Comparison of different photonic integration approaches for mid-infrared QCLs
Integration
approachIntegration
densityActive-passive
couplingHeat dissipation Process yield Current
performanceDetector
integrationMonolithic integration on InP ★★★ ★★★ ★★★ ★★★ ★★ ★★ Monolithic integration on Silicon ★★★ − ★★ ★ ★ ★★ Heterogeneous integration on silicon ★★★ ★★ ★★ ★★ ★ ★ Hybrid external cavity ★ ★ ★★★ ★★★ ★ − -
[1] Rothman L S, Gordon I E, Babikov Y, et al. The HITRAN2012 molecular spectroscopic database [J]. Journal of Quantitative Spectroscopy and Radiative Transfer, 2013, 130(1): 4-50. [2] Miller S E. Integrated optics: An introduction [J]. The Bell System Technical Journal, 1969, 48(7): 2059-2069. doi: 10.1002/j.1538-7305.1969.tb01165.x [3] Soref R. Mid-infrared photonics in silicon and germanium [J]. Nature Photonics, 2010, 4(8): 495-497. doi: 10.1038/nphoton.2010.171 [4] Lin H T, Luo Z Q, Gu T, et al. Mid-infrared integrated photonics on silicon: A perspective [J]. Nanophotonics, 2017, 7(2): 393-420. doi: 10.1515/nanoph-2017-0085 [5] Han Z, Lin P, Singh V, et al. On-chip mid-infrared gas detection using chalcogenide glass waveguide [J]. Applied Physics Letters, 2016, 108(14): 141106. doi: 10.1063/1.4945667 [6] Zhang K, Böhm G, Belkin M A. Mid-infrared microring resonators and optical waveguides on an InP platform [J]. Applied Physics Letters, 2022, 120(6): 061106. doi: 10.1063/5.0077394 [7] Faist J, Capasso F, Sivco D L, et al. Quantum cascade laser [J]. Science, 1994, 264(5158): 553-556. [8] Yang R Q. Infrared laser based on intersubband transitions in quantum wells [J]. Superlattices and Microstructures, 1995, 17(1): 77-83. doi: 10.1006/spmi.1995.1017 [9] Meyer J R, Bewley W W, Canedy C L, et al. The interband cascade laser [J]. Photonics, 2020, 7(3): 75. [10] Yao Y, Hoffman A J, Gmachl C F. Mid-infrared quantum cascade lasers [J]. Nature Photonics, 2012, 6(7): 432-439. doi: 10.1038/nphoton.2012.143 [11] Smit M, Williams K, Van Der Tol J. Past, present, and future of InP-based photonic integration [J]. APL Photonics, 2019, 4(5): 050901. doi: 10.1063/1.5087862 [12] Montoya J, Wang C, Goyal A, et al. Integration of quantum cascade lasers and passive waveguides [J]. Applied Physics Letters, 2015, 107(3): 031110. doi: 10.1063/1.4927430 [13] Jung S, Palaferri D, Zhang K, et al. Homogeneous photonic integration of mid-infrared quantum cascade lasers with low-loss passive waveguides on an InP platform [J]. Optica, 2019, 6(8): 1023-1030. doi: 10.1364/OPTICA.6.001023 [14] Wang R J, Taschler P, Wang Z X, et al. Monolithic integration of mid-infrared quantum cascade lasers and frequency combs with passive waveguides [J]. ACS Photonics, 2022, 9(2): 426-431. doi: 10.1021/acsphotonics.1c01767 [15] Faist J. Quantum Cascade Lasers[M]. Oxford: Oxford University Press, 2013. [16] Giewont K, Nummy K, Anderson F A, et al. 300-mm monolithic silicon photonics foundry technology [J]. IEEE Journal of Selected Topics in Quantum Electronics, 2019, 25(5): 18632360. [17] Nguyen-Van H, Baranov A N, Loghmari Z, et al. Quantum cascade lasers grown on silicon [J]. Science Reports, 2018, 8(1): 7206. doi: 10.1038/s41598-018-24723-2 [18] Loghmari Z, Rodriguez J B, Baranov A N, et al. InAs-based quantum cascade lasers grown on on-axis (001) silicon substrate [J]. APL Photonics, 2020, 5(4): 041302. doi: 10.1063/5.0002376 [19] Go R, Krysiak H, Fetters M, et al. InP-based quantum cascade lasers monolithically integrated onto silicon [J]. Optics Express, 2018, 26(17): 22389-22393. doi: 10.1364/OE.26.022389 [20] Wang Z, Abbasi A, Dave U, et al. Novel light source integration approaches for silicon photonics [J]. Laser & Photonics Reviews, 2017, 11(4): 1700063. [21] Roelkens G, Liu L, Liang D, et al. III-V/silicon photonics for on-chip and intra-chip optical interconnects [J]. Laser & Photonics Reviews, 2010, 4(6): 751-779. [22] Spott A, Peters J, Davenport M L, et al. Quantum cascade laser on silicon [J]. Optica, 2016, 3(5): 000545. doi: 10.1364/OPTICA.3.000545 [23] Spott A, Peters J, Davenport M L, et al. Heterogeneously integrated distributed feedback quantum cascade lasers on silicon [J]. Photonics, 2016, 3(2): 35. doi: 10.3390/photonics3020035 [24] Stanton E J, Spott A, Peters J, et al. Multi-spectral quantum cascade lasers on silicon with integrated multiplexers [J]. Photonics, 2019, 6(1): 6010006. [25] Radosavljevic S, Radosavljevic A, Schilling C, et al. Thermally tunable quantum cascade laser with an external germanium-on-SOI distributed Bragg reflector [J]. IEEE Journal of Selected Topics in Quantum Electronics, 2019, 25(6): 1200407.