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High performance strain-compensated 1.3μm MQW-PBH-LD using two-step etching
Published in Jong-Chun Woo, Yoon Soo Park, Compound Semiconductors 1995, 2020
H. S. Cho, D. H. Jang, J. K. Lee, J. S. Kim, K. H. Park, C. S. Park, H. M. Kim, K.-E. Pyun, H.-M. Park
In conclusion, we proposed and demonstrated two-step etching process for mesa formation that reduces the leakage current flowing out of active layer. It is shown that the performance of the fabricated MQW-PBH-LD using nonselective etching method is degraded severely at high temperature operation due to large leakage current through the p-p InP connection path. In the two-step etching method, however, low threshold current operation and high slope efficiency have been achieved. The minimum value of threshold current was 4.6mA and maximum slope efficiency was 0.32mW/mA at the lasing wavelength of 1.30μm for 320 μm-long uncoated laser diode. In comparing reverse leakage current of nonselective etched laser diode and that of two-step etched one, the leakage current of the latter was one order of magnitude lower than that of the former because smaller growth rate on the side wall of active region produced high resistive leakage current path through p-p InP connection.
Component Overview
Published in Kevin Robinson, Practical Audio Electronics, 2020
Laser Diodes – produce coherent, columnated (i.e. laser) light, rather than the less controlled emissions from a standard LED. Laser diodes have a wide variety of applications including such things as CD players and laser pointers.
Optics and Materials
Published in Lynne D. Green, Fiber Optic COMMUNICATIONS, 2019
A laser diode has a spectral width of 2 nm and a wavelength of 1550 nm. (a) What is the linewidth in MHz? (b) What is the spectral width as a percentage of the wavelength? (c) What is the linewidth as a percentage of the optical frequency?
Spatio-temporal variations of indoor air quality in a university library
Published in International Journal of Environmental Health Research, 2021
Veerendra Sahu, Bhola Ram Gurjar
Portable monitors based on light-scattering technology are efficient to collect large data of size-segregated PM concentration with high spatial and temporal resolution (Wang et al. 2019). Therefore, the portable GRIMM Aerosols Spectrometer (Model 1.109, GRIMM Aerosol Technik Gmbh & Co. KG, Ainring, Germany) was used to monitor mass concentration of various range of particulate matters (i.e. PM10, PM2.5 and PM1). This aerosols spectrometer works on the principle of light scattering. The spectrometer enables continuous and real–time measurements of airborne particle number concentration along with the particle size distribution in 31 size channels, ranging from 0.25 μm to 32 μm. The sampled air is drawn in to the measuring cell via inlet at 1.2 L/minute of flowrate through an internal compact volume flow-controlled pump. Laser diode produces the light pulse of wavelength in visible range at 655 nm. Scattering light pulse generated by each detected particle in sampled air is counted and the intensity of that light signal categorized to a specific particle size. The scattered light signal detected by another optics at scattering angle of 90 degrees and then recorded by receiver diode. Thereafter, particles from the sample are collected on 47 mm Polytetrafluoroethylene (PTFE) filter. The spectrometer calculates particle mass concentration by converting the particle size distribution data in to particle volume data and using GRIMM density correction (C) factor. C-factor varied for different dust types, default C-factor value (i.e. 1) is taken for present study.
Effect of relative humidity on the performance of five cost-effective PM sensors
Published in Aerosol Science and Technology, 2021
Peng Wang, Feng Xu, Huaqiao Gui, Huanqin Wang, Da-Ren Chen
The schematics of selected PM sensors, illustrating the optical arrangement and particle transport passage inside the sensors, are given in Figure 1. The solid lines in each layout represent the opening on the sensor’s cover, and the dotted dash lines are the borderlines of the transport passage and space occupied by particles. An injection-molded plastic chamber (in black) is utilized to house the particle transport passages, light source and photodetector, sampling fan and circuit board. No filter is applied before the sampling fan for the simplicity and cost reduction. The basic optical arrangement of a light scattering sensor consists of a light source for illuminating particles and a photodetector for measuring the intensity of photons scattered from single/multiple particles. A laser is utilized as the light source for all the selected PM sensors. The wavelength of the light is ∼650 nm for the sensors of LD12, LD16, SDS018 according to the vendor (not shown in the user manuals), and ∼660 and 658 nm for the sensors of SPS30 and OPC-N2, respectively, from their user manuals. Compared with infrared light-emitting diodes (LED), the wavelength spectrum of lights emitted from laser diodes is narrower. A solid-state photoelectric transducer is applied as the photon intensity detector. The “sensing volume” of a PM sensor is defined by the intersection between the optical path of the illuminating light and the particle stream. The optical arrangement of the light source and photodetector window is either in the 30° or 90° angle for the selected PM sensors. For the selected photometer-type PM sensors, only particles moving in a fraction of the transport passage cross-section are measured because the sensing volumes of sensors are not large enough to cover the entire cross-section of particle transport passage.
Bandgap tailoring and optical response of InAlAs/InGaAs/GaAsSb double quantum well heterostructures: the impact of uniaxial strain and well width variations
Published in Journal of Modern Optics, 2022
Md. Riyaj, Amit Rathi, A. K. Singh, P. A. Alvi
Bandgap tailoring is a powerful technique for the design and optimization of semiconductor heterostructures to obtain high-performance laser structures with characteristics such as low threshold current, longer wavelength and higher material gain. In a quantum well laser diode, when the carriers are in the optical region (i.e. active region), they can recombine radiatively for the process of photon amplification to occur [1–3]. As the optical gain is a function of the probability of occupation factor and carrier density, confinement of charge carriers is realized by a single or multiple quantum well active region materials separated by barrier layers. Since the energy bandgap of the barrier region material is larger, the light produced in the active region will not have an adequate amount of photon energy to be absorbed in them. In consequence, the non-radiative recombination rate shifts towards lower values, the radiative recombination rate shifts towards higher values and concurrently a fall in the recombination lifetimes is noticed [4–7]. When an external strain is applied, the mixing of wavefunctions between continuous sub-bands is reduced. It also affects the transition matrix elements [8–11]. To understand the nature of semiconductor optoelectronic devices, it is necessary to know their optical characteristics under different situations. If we apply an external field to the semiconductor heterostructure, the potential profiles are slanted and the positions of the energy states are changed. Therefore, the material gain spectra can be altered through an external field [12,13]. The field changes the band offsets and wavefunction forms, disfigures the electronic positions in the atoms or alters the crystal structure, resulting in the modification of the optical characteristics [14–18]. In semiconductor heterostructures, bandgap tailoring is an important design aid for optoelectronic devices [19–22]. In the present work, our motive behind this study of such nano-scale heterostructures is to attract attention to their potential applications in a variety of upcoming applications including optical tweezers and optical interconnects.