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10 pages, 1924 KiB

Open AccessEditor’s ChoiceCommunication

Processing-Speed Enhancement in a Delay-Laser-Based Reservoir Computer by Optical Injection

by Ziyue Li, Song-Sui Li, Xihua Zou, Wei Pan and Lianshan Yan

Photonics 2022, 9(4), 240; https://doi.org/10.3390/photonics9040240 - 4 Apr 2022

Cited by 4 | Viewed by 2105

Abstract

A delay-laser-based reservoir computer (RC) usually has its processing speed limited by the transient response of laser dynamics. Here, we study a simple all-optical approach to enhancing the processing speed by introducing optical injection to the reservoir layer of conventional RC that consists [...] Read more.

A delay-laser-based reservoir computer (RC) usually has its processing speed limited by the transient response of laser dynamics. Here, we study a simple all-optical approach to enhancing the processing speed by introducing optical injection to the reservoir layer of conventional RC that consists of a semiconductor laser with a delay loop. Using optical injection, the laser’s transient response effectively accelerates due to the speeded carrier-photon resonance. In the chaotic time-series prediction task, the proposed RC achieves good performance in a flexible range of injection detuning frequency under sufficient injection rate. Using proper injection parameters, the prediction error is significantly reduced and stabilized when using high processing speed. For achieving a prediction error below 0.006, the optical injection enhances the processing speed by an order of magnitude of about 5 GSample/s. Moreover, the proposed RC extends the advantage to the handwritten digit recognition task by achieving better word error rate. Full article

(This article belongs to the Special Issue Semiconductor Lasers)

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19 pages, 2857 KiB

Open AccessEditor’s ChoiceArticle

Parabola-Like Gold Nanobowtie on Sapphire Substrate as Nano-Cavity

by Wenbing Li, Zhuo Yang, Jiali Zhang, Xin Tong, Yuheng Zhang, Bo Liu and Chao Ping Chen

Photonics 2022, 9(3), 193; https://doi.org/10.3390/photonics9030193 - 17 Mar 2022

Cited by 2 | Viewed by 3774

Abstract

Plasmonic metallic nanostructures have attracted much interest for their ability to manipulate light on a subwavelength scale and for their related applications in various fields. In this work, a parabola-like gold nanobowtie (PGNB) on a sapphire substrate was designed as a nano-cavity for [...] Read more.

Plasmonic metallic nanostructures have attracted much interest for their ability to manipulate light on a subwavelength scale and for their related applications in various fields. In this work, a parabola-like gold nanobowtie (PGNB) on a sapphire substrate was designed as a nano-cavity for confining light waves in a nanoscale gap region. The near-field optical properties of the innovative PGNB structure were studied comprehensively, taking advantage of the time-resolved field calculation based on a finite-difference time-domain algorithm (FDTD). The calculation result showed that the resonance wavelength of the nano-cavity was quite sensitive to the geometry of the PGNB. The values that related to the scattering and absorption properties of the PGNB, such as the scattering cross section, absorption cross section, extinction cross section, scattering ratio, and also the absorption ratio, were strongly dependent on the geometrical parameters which affected the surface area of the nanobowtie. Increased sharpness of the gold tips on the parabola-like nano-wings benefited the concentration of high-density charges with opposite electric properties in the narrow gold tips with limited volume, thus, resulting in a highly enhanced electric field in the nano-cavity under illumination of the light wave. Reduction of the gap size between the two gold nano-tips, namely, the size of the nano-cavity, decreased the distance that the electric potential produced by the highly concentrated charges on the surface of each gold nano-tip had to jump across, therefore, causing a significantly enhanced field in the nano-cavity. Further, alignment of the linearly polarized electric field of the incident light wave with the symmetric axis of the PGNB efficiently enabled the free electrons in the PGNB to concentrate on the surface of the sharp gold tips with a high density, thus, strongly improving the field across the nano-cavity. The research provides a new insight for future design, nanofabrication, and characterization of PGNBs for applications in devices that relate to enhancing photons emission, improving efficiency for energy harvesting, and improving sensitivity for infrared detection. Full article

(This article belongs to the Special Issue Semiconductor Lasers)

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9 pages, 2081 KiB

Open AccessArticle

Laser Self-Mixing Sensor for Simultaneous Measurement of Young’s Modulus and Internal Friction

by Bo Wang, Bin Liu, Lei An, Pinghua Tang, Haining Ji and Yuliang Mao

Photonics 2021, 8(12), 550; https://doi.org/10.3390/photonics8120550 - 3 Dec 2021

Cited by 12 | Viewed by 2673

Abstract

The Young’s modulus and internal friction are two important parameters of materials. Self-mixing interferometry (SMI) is an emerging non-destructive sensing method that has been employed for various applications because of its advantages of simple structure, ease of alignment and high resolution. Some recent [...] Read more.

The Young’s modulus and internal friction are two important parameters of materials. Self-mixing interferometry (SMI) is an emerging non-destructive sensing method that has been employed for various applications because of its advantages of simple structure, ease of alignment and high resolution. Some recent works have proposed the use of SMI technology to measure the Young’s moduli and/or internal frictions by measuring the resonance frequencies and damping factors of specimen vibrations induced by impulse excitation. However, the measurement results may be affected by frequencies of SMI fringes, and the implementation requires extra signal processing on SMI fringes. In this work, we developed an all-fiber SMI system without SMI fringes to measure the Young’s modulus and internal friction simultaneously. Simulations and experiments were carried out to verify the feasibility of the proposed method. Two specimens of brass and aluminum were tested. The experimental results show that the standard deviations of Young’s moduli for brass and aluminum are 0.20 GPa and 0.14 GPa, and the standard deviations of internal frictions are

4.0 \times 10^{- 5}

and

5.4 \times 10^{- 5}

, respectively. This method eliminates the influences of the SMI fringe frequency on the resonant frequency and requires no signal processing on SMI fringes, contributing to its simplicity as a method for the measurement of the Young’s modulus and internal friction. Full article

(This article belongs to the Special Issue Semiconductor Lasers)

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11 pages, 3979 KiB

Open AccessArticle

Numerical Investigation and Design of Electrically-Pumped Self-Pulsing Fano Laser Based on III-V/Silicon Integration

by Yingming Zhao, Yu Li and Weiping Huang

Photonics 2021, 8(12), 530; https://doi.org/10.3390/photonics8120530 - 24 Nov 2021

Cited by 1 | Viewed by 2013

Abstract

A self-pulsing III-V/silicon laser is designed based on the Fano resonance between a bus-waveguide and a micro-ring resonator, partially covered by the graphene as a nonlinear saturable absorption component. The Fano reflector etched on the straight waveguide is used as one of the [...] Read more.

A self-pulsing III-V/silicon laser is designed based on the Fano resonance between a bus-waveguide and a micro-ring resonator, partially covered by the graphene as a nonlinear saturable absorption component. The Fano reflector etched on the straight waveguide is used as one of the cavity mirrors in the coupling region to work with the graphene induced loss and nonlinearity to achieve pulsed lasing in GHz repetition frequency. The detailed lasing characteristics are studied numerically by using the rate equation and finite-difference time-domain (FDTD) simulations. The results show that the CMOS compatible hybrid laser can generate picosecond pulses with repetition rate at 1~3.12 GHz, which increases linearly with the injection current. Full article

(This article belongs to the Special Issue Semiconductor Lasers)

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11 pages, 4396 KiB

Open AccessCommunication

Design and Optimization of 1.55 μm AlGaInAs MQW Polarization Mode Controllers

by Xiao Sun, Shengwei Ye, Bocang Qiu, Jichuan Xiong, Xuefeng Liu, John Marsh and Lianping Hou

Photonics 2021, 8(10), 422; https://doi.org/10.3390/photonics8100422 - 1 Oct 2021

Cited by 2 | Viewed by 3027

Abstract

A 1.55 μm AlGaInAs multi-quantum-well (MQW) ridge waveguide polarization mode controller (PMC) is proposed. The design is based on an asymmetric half-ridge waveguide structure in which the ridge is shallow etched on one side and has a deeply etched mesa structure on the [...] Read more.

A 1.55 μm AlGaInAs multi-quantum-well (MQW) ridge waveguide polarization mode controller (PMC) is proposed. The design is based on an asymmetric half-ridge waveguide structure in which the ridge is shallow etched on one side and has a deeply etched mesa structure on the other side. The Finite-Element Method (FEM) was used to simulate the PMC and optimize its structural parameters comprehensively. Furthermore, the fabrication tolerances were also investigated in detail. The optimized PMC has a polarization conversion efficiency (PCE) of around 92.5% with a half-beat length of 1250 μm. When the PMC length was fixed at 1250 μm, to achieve a PCE derivation less than 8%, the tolerances for the ridge waveguide width and shallow etch height were 1.60 μm to 1.65 μm and 2.13 μm to 2.18 μm, respectively. In order to reduce interband gap absorption loss, the quantum well intermixing (QWI) technique was used in the model to realize a blueshift (200 nm) in the PMC. QWI is a simple, flexible, and low-cost technique for fabricating a PMC integrated with a laser diode and reduces parasitic reflections, which would otherwise degrade the overall performance. QWI also eliminates MQW material anisotropy and alleviates the birefringence effect without the need for regrowth, achieving nearly uniform properties as a bulk material. Full article

(This article belongs to the Special Issue Semiconductor Lasers)

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9 pages, 2006 KiB

Open AccessArticle

Photonic Crystal Surface Emitting Laser Operating in Pulse-Periodic Regime with Ultralow Divergence Angle

by Ziye Wang, Cunzhu Tong, Lijie Wang, Huanyu Lu, Sicong Tian and Lijun Wang

Photonics 2021, 8(8), 323; https://doi.org/10.3390/photonics8080323 - 10 Aug 2021

Cited by 4 | Viewed by 3490

Abstract

The nanosecond-level pulse-operation characteristics of photonic-crystal surface-emitting lasers (PCSELs) with ultralow divergence were investigated in detail. We demonstrate a maximum peak output power of 14 W for a current pulse width of 9 ns, which is about 28 times the saturated power under [...] Read more.

The nanosecond-level pulse-operation characteristics of photonic-crystal surface-emitting lasers (PCSELs) with ultralow divergence were investigated in detail. We demonstrate a maximum peak output power of 14 W for a current pulse width of 9 ns, which is about 28 times the saturated power under continuous wave (CW) operation. The full width at half maximum (FWHM) of the optical response pulse is about 3 ns wider than the current pulse. The maximum repetition frequency reaches 400 kHz at 10 A without significant degradation of output power while the value is 100 kHz at 40 A. Moreover, the multimode behavior of the PCSEL at a high peak current was analyzed. Full article

(This article belongs to the Special Issue Semiconductor Lasers)

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12 pages, 4397 KiB

Open AccessArticle

Simulation of Photonic-Crystal Surface-Emitting Lasers with Air-Hole and Air-Pillar Structures

by Zi-Xian Yang, Chia-Yu Kuo and Gray Lin

Photonics 2021, 8(6), 189; https://doi.org/10.3390/photonics8060189 - 27 May 2021

Cited by 4 | Viewed by 3365

Abstract

Photonic-crystal surface-emitting lasers (PC-SELs), with and without regrowth, are theoretically simplified as air-hole and air-pillar structures, respectively. In this paper, square-latticed air-hole and air-pillar PC-SELs are simulated by a three-dimensional coupled-wave theory model and the design guideline is illustrated with a PC basis [...] Read more.

Photonic-crystal surface-emitting lasers (PC-SELs), with and without regrowth, are theoretically simplified as air-hole and air-pillar structures, respectively. In this paper, square-latticed air-hole and air-pillar PC-SELs are simulated by a three-dimensional coupled-wave theory model and the design guideline is illustrated with a PC basis of a right isosceles triangular and double circular shapes. The optimum PC filling factor is determined by infinite PC cavity analysis and the slope efficiency of finite-size PC-SEL is then calculated for the lowest threshold band-edge mode. In comparison with air-hole PC-SEL, air-pillar PC-SEL exhibits lower threshold gain, larger gain discrimination but lower slope efficiency. To achieve slope efficiency of comparable value, the cavity area of air-pillar PC-SEL is about four times larger than that of air-hole PC-SEL. Full article

(This article belongs to the Special Issue Semiconductor Lasers)

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12 pages, 4243 KiB

Open AccessArticle

Effective Failure Analysis for Packaged Semiconductor Lasers with a Simple Sample Preparation and Home-Made PEM System

by Tianyu Sun, Lei Qiao and Mingjun Xia

Photonics 2021, 8(6), 184; https://doi.org/10.3390/photonics8060184 - 24 May 2021

Viewed by 2941

Abstract

As the application requirements of semiconductor lasers continue to increase, severe challenges are brought to the reliability of semiconductor lasers. In order to promote the study of laser failure, this paper proposes an effective failure analysis method for packaged semiconductor lasers with a [...] Read more.

As the application requirements of semiconductor lasers continue to increase, severe challenges are brought to the reliability of semiconductor lasers. In order to promote the study of laser failure, this paper proposes an effective failure analysis method for packaged semiconductor lasers with a simple sample preparation and home-made photon emission microscopy (PEM) system. The new simple sample preparation process for failure analysis is presented and the necessary polishing fixture is designed so that sample can be obtained without expensive and complex micro-/nano-processing. Two types of home-made PEM experimental systems were established for observing the failure from the front facet and active region of semiconductor lasers. Experimental results showed that, with the proposed sample preparation flow, the home-made PEM experimental system effectively observed the leakage defects from the front facet and dark spot defects (DSDs) in the active region of semiconductor lasers. The method can help researchers and laser manufactures to perform effective failure analysis of packaged semiconductor lasers. Full article

(This article belongs to the Special Issue Semiconductor Lasers)

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12 pages, 6651 KiB

Open AccessArticle

Adaptive Gradient Estimation Stochastic Parallel Gradient Descent Algorithm for Laser Beam Cleanup

by Shiqing Ma, Ping Yang, Boheng Lai, Chunxuan Su, Wang Zhao, Kangjian Yang, Ruiyan Jin, Tao Cheng and Bing Xu

Photonics 2021, 8(5), 165; https://doi.org/10.3390/photonics8050165 - 19 May 2021

Cited by 8 | Viewed by 2558

Abstract

For a high-power slab solid-state laser, obtaining high output power and high output beam quality are the most important indicators. Adaptive optics systems can significantly improve beam qualities by compensating for the phase distortions of the laser beams. In this paper, we developed [...] Read more.

For a high-power slab solid-state laser, obtaining high output power and high output beam quality are the most important indicators. Adaptive optics systems can significantly improve beam qualities by compensating for the phase distortions of the laser beams. In this paper, we developed an improved algorithm called Adaptive Gradient Estimation Stochastic Parallel Gradient Descent (AGESPGD) algorithm for beam cleanup of a solid-state laser. A second-order gradient of the search point was introduced to modify the gradient estimation, and it was introduced with the adaptive gain coefficient method into the classical Stochastic Parallel Gradient Descent (SPGD) algorithm. The improved algorithm accelerates the search for convergence and prevents it from falling into a local extremum. Simulation and experimental results show that this method reduces the number of iterations by 40%, and the algorithm stability is also improved compared with the original SPGD method. Full article

(This article belongs to the Special Issue Semiconductor Lasers)

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Review

Jump to: Research

14 pages, 4206 KiB

Open AccessReview

Nano-grating Assisted Light Absorption Enhancement for MSM-PDs Performance Improvement: An Updated Review

by Narottam Das, Mohammad Nur-E-Alam, Alif Islam and Ain Zulaikha Maslihan Ain

Photonics 2021, 8(12), 539; https://doi.org/10.3390/photonics8120539 - 28 Nov 2021

Cited by 4 | Viewed by 3519

Abstract

The primary focus of this review article mainly emphasizes the light absorption enhancement for various nanostructured gratings assisted metal-semiconductor-metal photodetectors (MSM-PDs) that are so far proposed and developed for the improvement of light capturing performance. The MSM-PDs are considered as one of the [...] Read more.

The primary focus of this review article mainly emphasizes the light absorption enhancement for various nanostructured gratings assisted metal-semiconductor-metal photodetectors (MSM-PDs) that are so far proposed and developed for the improvement of light capturing performance. The MSM-PDs are considered as one of the key elements in the optical and high-speed communication systems for applications such as faster optical fiber communication systems, sensor networks, high-speed chip-to-chip interconnects, and high-speed sampling. The light absorption enhancement makes the MSM-PDs an ideal candidate due to their excellent performances in detection, especially in satisfying the high-speed or high-performance device requirements. The nano-grating assisted MSM-PDs are preordained to be decorous for many emerging and existing communication device applications. There have been a significant number of research works conducted on the implementation of nano-gratings, and still, more researches are ongoing to raise the performance of MSM-PDs particularly, in terms of enhancing the light absorption potentialities. This review article aims to provide the latest update on the exertion of nano-grating structures suitable for further developments in the light absorption enhancement of the MSM-PDs. Full article

(This article belongs to the Special Issue Semiconductor Lasers)

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