Search query: high power VCSEL array

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abstract: Optical neural networks offer radically new avenues for ultrafast, energy efficient hardware for machine learning and artificial intelligence. Reservoir Computing (RC) given its high performance and cheap training has attracted considerable attention for photonic neural network implementations, principally based on semiconductor lasers (SLs) Among SLs, Vertical Cavity Surface Emitting Lasers (VCSELs) possess unique attributes, e.g. high speed, low power, rich dynamics, reduced cost, ease to integrate in array architectures, making them valuable candidates for future photonic neural networks. This work provides a comprehensive analysis of a telecom wavelength GHz rate VCSEL RC system, revealing the impact of key system parameters on its performance across different processing tasks.
author_names: Julian Bueno

Joshua Robertson

Matej Hejda

Antonio Hurtado
title: Comprehensive Performance Analysis of a VCSEL Based Photonic Reservoir Computer
venue: IEEE Photonics Technology Letters
year: 2021

abstract: A face pumped Nd:YAG slab laser with high power output and temperature fluctuation adaptability is proposed and demonstrated for the first time. A two dimensional (2D) vertical cavity surface emitting laser (VCSEL) array at 808 nm with a low wavelength shift coefficient is used as the pump source with a total pump power of 1.38 kW. The array is cooled by a double layer vascularized macro channel heat sink for effective heat management. A 1064 nm maximum power of 437 W from the slab laser is obtained by optimizing the output coupling, and the power variation is only 4.9% over the temperature range from 16 degC to 34 degC. The results show that the high power slab laser pumped by VCSEL has an excellent performance in temperature tolerance and lower requirements for coolant, which is only water cooled by the macro channel heat sink and no need for deionized water; it also provides a solution for high power lasers used in the complicated environment. Furthermore, it is possible to scale the output power to ~kW level by further increasing the VCSEL pump power.
author_names: Peng-Cheng Di

Xue-peng Li

Rujia Wang

Xiao-Jun Wang

Da-Fu Cui

Qin-Jun Peng
title: High Power VCSEL Pumped Slab Laser With Temperature Fluctuation Adaptability
venue: IEEE Photonics Technology Letters
year: 2021

abstract: Applying a reverse bias near the breakdown voltage results in photon emission at the pn junction in vertical cavity surface emitting lasers (VCSELs) This radiation can be collected with an emission microscope. Here, this technique is employed to investigate a high power two dimensional (2D) VCSEL array with a large number of emitters at a non degraded state and after high electrical stress. It has been found that non degraded arrays show varying photon intensities across all emitters at breakdown condition while degraded arrays exhibit more intense electroluminescence at areas with faulty emitters containing defects in the active area as confirmed by plan view scanning transmission electron microscopy analysis.
author_names: Roberto Cesco Fabbro

Thomas Haber

Gernot Fasching

Raffaele Coppeta

Michael Pusterhofer

W Grogger
title: Defect localization in high power vertical cavity surface emitting laser arrays by means of reverse biased emission microscopy
year: 2021

abstract: In this work, we demonstrate a novel high power vertical cavity surface emitting laser (VCSEL) array with highly single mode (SM) and single polarized output performance without significantly increasing the intra cavity loss and threshold current (Ith) By combining a low loss zinc diffusion aperture with an electroplated copper substrate, we can obtain a highly SM output (side mode suppression ratio >50dB) with a very narrow divergence angle (1/e2:~10) under high output power (3.1 W; 1% duty cycle) and sustain a single polarization state, with a polarization suppression ratio of around 9 dB, under the full range of bias currents. Compared to the reference device without the copper substrate, the demonstrated array can not only switch the output optical spectra from quasi SM to highly SM but also maintain a close threshold current value (Ith: 0.8 versus 0.7 mA per unit device) and slope efficiency. The enhancement in fundamental mode selectivity of our VCSEL structure can be attributed to the single polarized lasing mode induced by tensile strain, which is caused by the electroplated copper substrate, as verified by the double crystal x ray measurement results.
author_names: Jin-Wei Shi

Zuhaib Khan

Ray-Hua Horng

Hsiao-Yun Yeh

Chun-Kai Huang

Cheng-Yi Liu

Jie-Chen Shih

Yung-Hao Chang

J L Yen

Jinn-Kong Sheu
title: High power and single mode VCSEL arrays with single polarized outputs by using package induced tensile strain.
venue: Optics letters
year: 2020

abstract: Novel 940 nm (quasi )coherent VCSEL array (3x3) is demonstrated. It exhibits high power (62.4 mW) single spot output with narrow divergence angle ~5deg) over the full range of bias currents, and wide 3 dB E 0 bandwidth (10 GHz)
author_names: Zuhaib Khan

Jie-Chen Shin

Yung-Hao Chang

Jin-Wei Shi
title: High Brightness and High Speed Coherent VCSEL Array
venue: 2020 Conference on Lasers and Electro Optics (CLEO)
year: 2020

abstract: Abstract In this paper, we investigated high power selectively oxidation confined AlxGa1 xAs/GaAs 850 nm vertical cavity surface emitting laser (VCSEL) and fabricated two dimensional VCSEL arrays by photolithography using photo masks. Inductively coupled plasma (ICP) was employed to create the deep platform during the mesa process. The number of illuminating lasers has been designed at 60, 85, and 109 in the array. We further studied the influence of the number of illuminating lasers on the characteristics of the VCSEL devices. The threshold current was found to be increased significantly at about 93 mA, 118 mA, and 149 mA, respectively. The injection current should produce a greater than the critical current density to meet the criteria for population inversion. However, the corresponding voltage remained almost unchanged, in the range of 1.57 1.63 V. The maximum optical output power was increased even more appreciably. It was measured at 448 mW, 592 mW, and 746 mW, respectively. On the other hand, the device equivalent series resistance was decreased with more illumination lasers in the array. The averaged resistance has been estimated at 4.16 O, 3.14 O, and 2.47 O, respectively. In addition, the optical spectrum became more dispersed, showing more lasing modes for the samples with the highest number in illumination lasers in the array. The peak wavelength full width at half maximum was also slightly increased. The related electro optical characteristics have been summarized and further discussed.
author_names: G M Wu

F C Kung

Chiau Yeng Lee
title: Study of fabrication and characterization of high power 850 nm vertical cavity surface emitting laser arrays
year: 2020

abstract: High power vertical cavity surface emitting laser (VCSEL) arrays with multiple emitters have been receiving remarkable attention currently due to their emerging applications in consumer market such as 3D sensing illumination laser source in mobile devices as well as in automotive LIDAR applications. Failure mode analysis will help provide useful information for VCSEL array design and process improvement. However, using solely general physical failure analysis techniques is insufficient. The challenge of failure mechanism study is how to locate and capture the small physical defects in the early stage since it may randomly occur in the entire active region of the emitter This work developed 3D transmission electron microscopy (TEM) method, that is, planar view TEM together cross section TEM, to investigate failure mode phenomenon in this kind of high power VCSEL arrays. Overstressed reliability testing intentionally create failure in VCSEL arrays where dim emitters are found. Optical microscope images can't see any abnormality while infrared microscope can catch small 'mouse bite' abnormality at oxide aperture. Planar view TEM method is developed to isolate the target dim emitter and trim away most of the top and bottom DBR layers to keep the oxide layer and active region to thin enough where 200KV electron beam can penetrate planar view lamella. The whole oxide aperture is achieved and scanning TEM images clearly show the 'flower like' oxide blasters at oxide aperture periphery. It is from further oxidation of the oxide tip. Cross section TEM reveal the oxide layer morphology where the further oxidation layer from oxide tip is thinner than the original oxide layer. The oxide tip further oxidation is possibly due to non reaction steam in existence in the oxide causing the second oxidation of oxide layer during overstress test. This work demonstrate that 3D TEM method is good technique to catch small physical failure features in VCSEL arrays, which will help to analyze failure mode in high power VCSEL arrays for 3D sensing application.
author_names: Xiaoyan Wang

Jefferson M Abrenica

Patrick Koh
title: 3D transmission electron microscopy method development for failure analysis in VCSEL arrays
venue: Photonics Europe
year: 2020

abstract: We present the design and test results of a 4 channel 10 Gbps/ch Vertical Cavity Surface Emitting Laser array driver, the cpVLAD. With on chip charge pumps to extend the biasing headroom for the VCSELs needed for low temperature operation and mitigation of the radiation effects. The cpVLAD was fabricated in a 65 nm CMOS technology. The test results show that the cpVLAD is capable of driving VCSELs with forward bias voltages as high as 2.8 V from a 2.5 V power supply. The power consumption of the cpVLAD is 94 mW/ch.
author_names: X Huang

Datao Gong

Q Sun

Chong-shun Chen

Di Guo

Suen Ray Hou

G Huang

Szymon Kulis

C Liu

T Liu

Paulo Moreira

A S'anchez Rodr'iguez

H L Sun

Jan Troska

L Xiao

Longkun Zhang

W Zhang

J Ye
title: A 4 Channel 10 Gbps/ch CMOS VCSEL Array Driver with on chip Charge Pumps
year: 2020

abstract: Future ultra broadband and low latency radio access networks pose stringent specifications for time synchronizations. For 5G base stations, inter site timing error should be 130ns for carrier aggregation and <10ns for high accuracy positioning [1] requiring a 10 10 level relative drift for a 1min clock holdover. Meanwhile, massive deployments of compact access nodes also make small size, power, and cost indispensable for clocks. Oven controlled crystal/MEMS oscillators (OCXO/OCMO) with moderate cost are currently used. But, their resonators exhibit long term aging and high temperature sensitivity 31ppm/K for MEMS resonators) hence requiring up to a watt level heater power for temperature stabilization. Referencing clocks to invariant physical constants well solves the drifting issue. To this end, chip scale atomic (Cs or Rb) clocks (CSACs) [2] [4] have achieved outstanding stability, low power (120mW in [3] and miniaturization. However, the highly complicated optical electrical components (e.g. VCSEL laser with high wavelength accuracy) integration, and packaging (e.g. heater with mK accuracy temperature control, magnetic shield, buffer gas) lead to very high cost 1k) [3] Recently, molecular clock referenced to sub THz rotational transitions of carbonyl sulfide (OCS) gas emerged as a fully electronic solution with high stability [5] In particular, chip scale molecular clock (CSMC) built using a CMOS chip coupled with a waveguide OCS molecular cell, appeared as highly attractive for miniaturization and significant cost reduction. In [5] the long term stability (3.8x10 10@averaging time \tau=10^ 3}\mathrm{S} of the CSMC was limited by the non ideal measured OCS transition curve, which is susceptible to environmental disturbance. This paper presents a 70mW CSMC chip design that enables high order dispersion curve locking and enhances the long term stability by 9x. Additional testing results also reveal its advantages in temperature stability over OCXO/OCMO and magnetic sensitivity over CSAC, respectively.
author_names: Cheng Wang

Xiang Yi

Mina Kim

Ruonan Han
title: 29.5 Sub THz CMOS Molecular Clock with 43ppt Long Term Stability Using High Order Rotational Transition Probing and Slot Array Couplers
venue: 2020 IEEE International Solid State Circuits Conference (ISSCC)
year: 2020

abstract: Metal grids are used to solve the current spreading problem in coherently coupled implant defined vertical cavity surface emitting laser (VCSEL) arrays. In phase mode operation with a near diffraction limited beam is achieved in hexagonal 19 element arrays. The measured beamwidth of the arrays is as low as 1.3deg, which is only about 1.08 times of the diffraction limit. The arrays can maintain a relatively high proportion of 29.2% average power in the central lobe from threshold to maximum output power. The narrow beamwidth and high power proportion benefit from the uniform near field optical intensity owing to the metal grids. This technique provides an alternative method to realize large area in phase coherently coupled VCSEL array with high beam quality.
author_names: Guanzhong Pan

Yiyang Xie

Chen Xu

Qiuhua Wang

Yibo Dong

Jun Deng

Hongda Chen

Jie Sun
title: In Phased Implant Defined Hexagonal VCSEL Array With Near Diffraction Limited Beam
venue: IEEE Photonics Technology Letters
year: 2019