/pdf/diode-pumped-wideband-thulium-doped-fiber-amplifiers-for-5djww58w6f.pdf

Diode-pumped Wideband Thulium-doped Fiber Amplifiers for Optical Communications in the 1800 - 2050 nm Window

Broadband Photodetector Based on Inorganic Perovskite CsPbBr3/GeSn Heterojunction

The availability of high-frequency pulsed emitters in the 2–2.5 μm wavelength range paved the way for a wealth of new applications in ultrafast spectroscopy, free-space and fiber-optical communications, surveillance and recognition, artificial intelligence, and medical imaging. However, developing these emerging technologies and their large-scale use depend on the availability of high-speed, low-noise, and cost-effective photodetectors. With this perspective, here we demonstrate GeSn photodiodes grown on silicon wafers featuring a high broadband operation covering the extended-SWIR range with a peak responsivity of 0.3 A/W at room temperature. These GeSn devices exhibit a high bandwidth reaching 7.5 GHz at 5 V bias with a 2.6 μm cutoff wavelength, and their integration in ultrafast time-resolved spectroscopy applications is demonstrated. In addition to enabling time-resolved electroluminescence at 2.3 μm, the high-speed operation of GeSn detectors was also exploited in the diagnostics of ultrashort pulses of a supercontinuum laser with a temporal resolution in the picosecond range at 2.5 μm. Establishing these capabilities highlights the potential of manufacturable GeSn photodiodes for silicon-integrated high-speed extended-SWIR applications. 

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High-Bandwidth Extended-SWIR GeSn Photodetectors on Silicon Achieving Ultrafast Broadband Spectroscopic Response

We report an investigation on the photo-response from a GeSn-based photodetector using a tunable laser with a range of incident light power. An exponential increase in photocurrent and an exponential decay of responsivity with increase in incident optical power intensity were observed at higher optical power range. Time-resolved measurement provided evidence that indicated monomolecular and bimolecular recombination mechanisms for the photo-generated carriers for different incident optical power intensities. This investigation establishes the appropriate range of optical power intensity for GeSn-based photodetector operation.

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Power-Dependent Investigation of Photo-Response from GeSn-Based p-i-n Photodetector Operating at High Power Density

The Sn composition graded GeSn layer with Sn content increased from 11% to 14.3% was grown on a Si substrate by molecular beam epitaxy. The structural properties of the GeSn layer are investigated, and the film is gradually relaxed along the thickness, reaching approximately 71.6%. The GeSn p–i–n detectors were fabricated by using a complementary metal oxide semiconductor compatible process. The GeSn detectors demonstrated a cutoff wavelength of approximately 3.3 μm at room temperature with a dark current of 0.3 A/cm 2 @ -1 V. At a wavelength of 2000 nm, the GeSn detectors had a responsivity of 110 mA/W and -3 dB bandwidth ( f 3 dB ) about 3 GHz. These results suggest that high Sn content relax GeSn can be grown by MBE and paves the way toward the feasibility of mid-infrared GeSn photonics. 

Sn composition graded GeSn photodetectors on Si substrate with cutoff wavelength of 3.3 μm for mid-infrared Si photonics

We report the demonstration of a normal-incidence p-i-n germanium-tin (Ge0.951Sn0.049) photodetector on silicon-on-insulator substrate for 2 μm wavelength application. The DC and RF characteristics of the devices have been characterized. A dark current density under −1  V bias of approximately 125  mA/cm2 is achieved at room temperature, and the optical responsivity of 14 mA/W is realized for illumination wavelength of 2 μm under −1  V reverse bias. In addition, a 3 dB bandwidth (f3 dB) of around 30 GHz is achieved at −3  V, which is the highest reported value among all group III–V and group IV photodetectors working in the 2 μm wavelength range. This work illustrates that a GeSn photodetector has great prospects in 2 μm wavelength optical communication.

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30 GHz GeSn photodetector on SOI substrate for 2 µ m wavelength application

High-speed avalanche photodiodes (APDs) have attracted great interest for their potential applications in weak signal detection and free-space communication. In this article, the bandwidth characteristics of mid-wavelength infrared (MWIR) Hg0.7Cd0.3 Te electron-APDs (e-APDs) are investigated by the Monte Carlo method. The simulated gain, excess noise, and carrier velocity agree well with the previously reported experimental data. Moreover, the transport process of photogenerated carriers is described in detail. Meanwhile, the effects of different absorption region thickness as well as the incident wavelengths on the device bandwidth are studied, and the trend of the bandwidth with bias voltage is explained. Finally, a structure with gradient <inline-formula> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula>-region is proposed to further increase the bandwidth.

Monte Carlo Simulation of High-Speed MWIR HgCdTe e-APD

In this paper, a vertical stacked near-infrared (NIR) and extended short wavelength infrared (eSWIR) dual-band detector based on InGaAs and In0.53Ga0.47As/GaAs0.5Sb0.5 type-II superlattice (T2SL) is presented. A barrier layer of AlAs0.56Sb0.44 allows the independent working of the two sub-detectors. The InGaAs NIR sub-detector operates under positive bias, while the eSWIR band detector operates under reverse bias. The NIR sub-detector shows a dark current density of 7.35 × 10−5 A/cm2 under the bias of 0.1 V, the responsivity of 0.88 A/W, and a specific detectivity of 4.69 × 1011 cm· Hz1/2/W at 1510 nm. Meanwhile, the dark current density of eSWIR sub-detector is 8.68 × 10−4 A/cm2 under −0.4 V with the corresponding responsivity of 0.21 A/W, and a specific detectivity of 1.85×1010 cm·Hz1/2/W at 2 μm. Furthermore, a single-pixel imaging system is built to demonstrate the capability of dual-band detectors in information capturing and target recognition.

High-Performance InP-Based Bias-Tunable Near-Infrared/Extended-Short Wave Infrared Dual-Band Photodetectors

High-speed photodetectors operating at mid-wave infrared are crucial for free-space optical communication and frequency comb spectroscopy. In this letter, we report a high-speed mid-wave infrared uni-traveling carrier photodiode based on InAs/InAsSb type-II superlattice at room temperature for the first time. The device exhibits a cut-off wavelength of around 5.5 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> at room temperature. The responsivity of the device is about 0.6 A/W (at 4.5 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>) under −1 V at room temperature. The frequency response of the device is characterized by an optical parametric amplification system generating mid-infrared femtosecond pulses. A device with a 20 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> diameter has a 3-dB bandwidth of 12.8 GHz at −4 V. These promising results suggest that the device could be potential candidates to be employed in the emerging high-speed MWIR applications.

High-Speed Mid-Wave Infrared Uni-Traveling Carrier Photodetector Based on InAs/InAsSb Type-II Superlattice

In this article, we studied two high-speed mid-wave infrared InAs/InAsSb type-II superlattice (T2SL) uni-traveling carrier (UTC) photodetectors (PDs) with different graded p-doping profiles in the absorber. It is found that the UTC device with higher absorber p-doping (hereafter referred to as Device A) has a larger 3-dB bandwidth than that of the device with lower absorber p-doping (hereafter referred to as Device B). However, Device A shows a higher dark current and lower responsivity performance than Device B. The peak responsivity of Devices A and B is about 0.9 and 1.2 A/W, respectively, under −1 V at room temperature. The performance comparisons of both devices are explored in detail. These results could contribute a further step toward developing high-speed InAs/InAsSb T2SL PDs.

Zhiqi Zhou

Papers

30 GHz GeSn photodetector on SOI substrate for 2 µ m wavelength application

Monte Carlo Simulation of High-Speed MWIR HgCdTe e-APD

High-Performance InP-Based Bias-Tunable Near-Infrared/Extended-Short Wave Infrared Dual-Band Photodetectors

High-Speed Mid-Wave Infrared Uni-Traveling Carrier Photodetector Based on InAs/InAsSb Type-II Superlattice

High-Speed Mid-Wave Infrared InAs/InAsSb Superlattice Uni-Traveling Carrier Photodetectors With Different Absorber Doping