Browsing by Author "Chang, Hsiang-Szu"

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Enhancement in speed and responsivity of uni-traveling carrier photodiodes with GaAs0.5Sb0.5/In0.53Ga0.47As type-II hybrid absorbers
(2019-05-27)
Naseem
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Ahmad, Zohauddin
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Chao, Rui-Lin
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Chang, Hsiang-Szu
;
Ni, C-J
We demonstrate a top-illuminated high-speed uni-traveling carrier photodiode (UTC-PD) with a novel design in the p-type absorber, which call effectively shorten the photon absorption depth at telecommunication wavelengths (1.31 similar to 1.55 mu m) and further enhance the bandwidth-efficiency product of UTC-PD. In our proposed new UTC-PD structure, the p-type In0.53Ga0.47As absorption layer is replaced by the type-II GaAs0.5Sb0.5 (p)/In0.53Ga0.47As (i) hybrid absorber. Due to the narrowing of the bandgap and enhancement of the photo-absorption process at the type-II interface between the GaAs0.5Sb0.5 and In0.53Ga0.47As layers, our device shows an over 16.7% improvement in the responsivity compared with that of UTC-PD with the same thickness of pure In0.53Ga0.47As absorber (0.7 mu m) and a zero optical coupling loss. Our demonstrated device with a simple top-illuminated structure offers a large active mesa (25 mu m). a wide optical-to-electrical (O-E) bandwidth (33 GHz), a high responsivity (0.7 A/W), and a high saturation current (>5 mA) under 1.31 mu m optical wavelength. These promising results suggest that our proposed PD structure can fundamentally overcome the trade-off among bandwidth. efficiency. and device active diameter of high-speed PDs. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Enhancing luminescence efficiency of InAs quantum dots at 1.5 mu m using a carrier blocking layer
(2006-07-31)
Hsieh, Tung-Po
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Chiu, Pei-Chin
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Chyi, Jen-Inn
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Chang, Hsiang-Szu
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Chen, Wen-Yen
The authors report an effective way to enhance the optical efficiency of InAs quantum dots (QDs) on GaAs emitting at the wavelength of 1.5 mu m. It is found that the loss of holes from QDs to their proximity via the high indium composition InGaAs overgrown layer, which is necessary for achieving long wavelength emission, is the origin of photoluminescence intensity degradation at high temperature. Inserting a 4 nm thick Al0.45Ga0.55As layer, acting as a carrier blocking layer, into the GaAs capping matrix can improve the room temperature photoluminescence peak intensity by five and two times for the ground and first excited states, respectively.
High-Speed In0.52Al0.48As Based Avalanche Photodiode With Top-Illuminated Design for 100 Gb/s ER-4 System
(2018-12-01)
Wu, Song-Lin
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Naseem
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Wun, Jhih-Min
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Chao, Rui-Lin
;
Huang, Jack Jia-Sheng
High-speed top-illuminated avalanche photodiodes (APDs) with large diameters (25 mu m) are demonstrated for the application of 4-channels 100 Gb/s data rate. They achieve a bandwidth of 17 GHz at low-gain (M-G = 6.2; 3.6 A/W) and large-gain bandwidth (responsivity bandwidth) product (410 GHz (237.8 GHz-A/W); 55% external efficiency at the unit gain) while maintaining invariant high speed (14 GHz) under high power (0.5 mW) and 0.9 V-b(r) operations. By packaging the demonstrated APD with a 25 Gb/s transimpedance amplifier in a 100 Gb/s ROSA package, a good sensitivity of around -20.6 dBm optical modulation amplitude (OMA) at the data rate of 25.78 Gb/s has been successfully demonstrated. The achieved sensitivity not only meets the required receiver sensitivity (-18.5 dBm OMA) in 100 GbE-ER-4 Lite (40 km) system, it is also comparable with that of the high-performance 1(N) Gb/s ROSA incorporated with the backside illuminated APD design. Overall, our novel APD structure can eliminate the costly flip-chip bonding package in the 100 Gb/s ROSA without sacrificing its sensitivity performance.
Low-density quantum dots embedded in photonic-crystal nanocavities for single-photon generations
(2007)
Chang, Wen-Hao
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Chen, Wen-Yen
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Chang, Hsiang-Szu
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Hsieh, Tung-Po
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Chyi, Jen-Inn
An efficient single-photon source based on low-density InGaAs quantum dots in a photonic-crystal nanocavity is demonstrated. The single-photon source features the effects of photonic band gap, yielding a single-mode spontaneous emission coupling efficiency as high as beta=92% and a linear polarization degree up to p=95%. This appealing performance makes it well-suited for practical implementation of polarization-encoded schemes in quantum cryptography.
Origins of nonzero multiple photon emission probability from single quantum dots embedded in photonic crystal nanocavities
(2009-04-20)
Chang, Hsiang-Szu
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Chen, Wen-Yen
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Hsu, Tzu-Min
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Hsieh, Tung-Po
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Chyi, Jen-Inn
This work explores the origins of nonzero multiphoton emission probability for quantum dots embedded in photonic crystal nanocavities using different excitation energies to inject excitons into either the GaAs barrier or the quantum-dot excited state. The detected multiphoton events are established to arise from both the recapture of excitons and background emissions from the wetting layer tail states. The exciton emission is analyzed using rate-equation calculations, which suggest that multiphoton emission is dominated by the recapture effect.
Single photon emission from an InGaAs quantum dot precisely positioned on a nanoplane
(2007-02-12)
Hsieh, Tung-Po
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Chyi, Jen-Inn
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Chang, Hsiang-Szu
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Chen, Wen-Yen
;
Hsu, Tzu Min
This work demonstrates single photon emissions from a site-controlled quantum dot (QD) grown on a self-constructed nanoplane. The size of the nanoplane on the micron-sized multifacet structure is accurately controlled by a low surface reducing rate (similar to 16 nm/min). Single QD spectral lines were resolved and identified. The antibunching behavior reveals that single photons are emitted from the positioned QD. (c) 2007 American Institute of Physics.
Top-Illuminated In0.52Al0.48As-Based Avalanche Photodiode With Dual Charge Layers for High-Speed and Low Dark Current Performances
(2018-03-01)
Chen, Yi-Han
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Wun, Jhih-Min
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Wu, Song-Lin
;
Chao, Rui-Lin
;
Huang, Jack Jia-Sheng
A novel type of top-illuminated, etch-mesa In0.52Al0.48 As-based avalanche photodiode (APD) with high-speed (>25 Gb/s), low dark current performance has been demonstrated. The 25G APD device is composed of n-side down design with the In0.52Al0.48As multiplication (M) layer buried at the bottom to avoid the issues of surface breakdown and complex guard ring structure. In addition, we demonstrate that the new structure with two charge layers and triple mesas can effectively confine the electric-field within the center of M-layer and minimize the edge breakdown around the periphery of mesa. In contrast to the costly flip-chip bonding package with backside illumination, our demonstrated device is based on a simple top-illuminated structure that includes a large active diameter of 30 mu m for easy optical alignment, a reasonable punch-through responsivity (0.7 A/W at 1.31 mu m wavelength), and a good 3-dB optical-to-electrical (O-E) bandwidth (22.5 GHz) under low gain operations (M-G = similar to 3). Furthermore, it can sustain the 3-dB bandwidth of 15 GHz over a wide range of launched optical power (-17 to + 4.6 dBm) under a moderate gain (M-G = similar to 5) operation at 1.31 mu m wavelength. High-sensitivity (-16 dBm) for error-free 28 Gb/s operation can also be achieved at 1.55 mu m wavelength.