225 research outputs found
Structured metal/polymer back reflectors for III-V solar cells
We report on fabrication of microstructured metal/polymer back reflectors for light trapping in III-V solar cells. The asymmetric triangular grating provided the highest diffraction of the light when compared to half sphere and cylinder reflectors
Nanostructures for light management in thin-film GaAs quantum dot solar cells
We have investigated structures for thin-film GaAs quantum dot solar cells. Light trapping at quantum dot bands is realized by a triangular grating reflector whose aspect ratio is identified as the main design parameter
1.4 µm continuous-wave diamond Raman laser
The longest wavelength (~1.4 µm) emitted by a diamond Raman laser pumped by a semiconductor disk laser (SDL) is reported. The output power of the intracavity-pumped Raman laser reached a maximum of 2.3 W with an optical conversion efficiency of 3.4% with respect to the absorbed diode pump power. Narrow Stokes emission (FWHM 40 nm was achieved via rotation of an intracavity birefringent filter that tuned the SDL oscillation wavelength
Widely tunable 2 m hybrid laser using GaSb semiconductor optical amplifiers and Si3N4 photonics integrated reflector
Tunable lasers emitting at a 2-3 m wavelength range and compatible with
photonic integration platforms are of great interest for sensing applications.
To this end, combining GaSb-based semiconductor gain chips with SiN
photonic integrated circuits offers an attractive platform. Herein, we exploit
the low-loss features of SiN waveguides and demonstrate a hybrid laser
comprising a GaSb gain chip with an integrated tunable SiN Vernier
mirror. At room temperature, the laser exhibited a maximum output power of 15
mW and a tuning range of 80 nm (1937-2017 nm). The low-loss performance of
several fundamental SiN building blocks for photonic integrated
circuits is also validated. More specifically, the single-mode waveguide
exhibit transmission loss as low as 0.15 dB/cm, the 90 bend has 0.008
dB loss, and the 50/50 Y-branch has an insertion loss of 0.075 dB
Sub-100 ps monolithic diamond Raman laser emitting at 573 nm
We report a compact and efficient picosecond diamond Raman laser at 573 nm wavelength. The laser consists of a 0.5 mm thick single-crystal synthetic diamond coated to form a plane–plane laser resonator, and pumped at 532 nm by a frequency-doubled Q-switched microchip laser system. The pump delivers 85 ps pulses at 100 kHz repetition rate at a maximum average power of ~500 mW. We demonstrate 1st Stokes emission from the diamond Raman laser with maximum power of 175 mW, corresponding to a conversion efficiency of 47% and a pulse duration of 71 ps. Substantial pulse shortening is obtained by proper adjustment of the pump spot diameter on the diamond sample. A minimum pulse duration of 39 ps is reported for a conversion efficiency of 36% and 150 mW output power. The simplicity of the architecture makes the system highly appealing as a yellow picosecond laser source
Multi-type quantum well semiconductor membrane external-cavity surface-emitting lasers (MECSELs) for widely tunable continuous wave operation
Membrane external-cavity surface-emitting lasers (MECSELs) are at the
forefront of pushing the performance limits of vertically emitting
semiconductor lasers. Their simple idea of using just a very thin (hundreds of
nanometers to few microns) gain membrane opens up new possibilities through
uniform double side optical pumping and superior heat extraction from the
active area. Moreover, these advantages of MECSELs enable more complex band gap
engineering possibilities for the active region by the introduction of multiple
types of quantum wells (QWs) to a single laser gain structure. In this paper,
we present a new design strategy for laser gain structures with several types
of QWs. The aim is to achieve broadband gain with relatively high power
operation and potentially a flat spectral tuning range. The emphasis in our
design is on ensuring sufficient gain over a wide wavelength range, having
uniform pump absorption, and restricted carrier mobility between the different
quantum wells during laser operation. A full-width half-maximum tuning range of
> 70 nm (> 21.7 THz) with more than 125 mW of power through the entire tuning
range at room temperature is demonstrated
Excitation energy-dependent nature of Raman scattering spectrum in GaInNAs/GaAs quantum well structures
The excitation energy-dependent nature of Raman scattering spectrum, vibration, electronic or both, has been studied using different excitation sources on as-grown and annealed n- and p-type modulation-doped Ga(1 − x)In(x)N(y)As(1 − y)/GaAs quantum well structures. The samples were grown by molecular beam technique with different N concentrations (y = 0%, 0.9%, 1.2%, 1.7%) at the same In concentration of 32%. Micro-Raman measurements have been carried out using 532 and 758 nm lines of diode lasers, and the 1064 nm line of the Nd-YAG laser has been used for Fourier transform-Raman scattering measurements. Raman scattering measurements with different excitation sources have revealed that the excitation energy is the decisive mechanism on the nature of the Raman scattering spectrum. When the excitation energy is close to the electronic band gap energy of any constituent semiconductor materials in the sample, electronic transition dominates the spectrum, leading to a very broad peak. In the condition that the excitation energy is much higher than the band gap energy, only vibrational modes contribute to the Raman scattering spectrum of the samples. Line shapes of the Raman scattering spectrum with the 785 and 1064 nm lines of lasers have been observed to be very broad peaks, whose absolute peak energy values are in good agreement with the ones obtained from photoluminescence measurements. On the other hand, Raman scattering spectrum with the 532 nm line has exhibited only vibrational modes. As a complementary tool of Raman scattering measurements with the excitation source of 532 nm, which shows weak vibrational transitions, attenuated total reflectance infrared spectroscopy has been also carried out. The results exhibited that the nature of the Raman scattering spectrum is strongly excitation energy-dependent, and with suitable excitation energy, electronic and/or vibrational transitions can be investigated
Dilute nitride and GaAs n-i-p-i solar cells
Abstract
We demonstrate for the first time the operation of GaInNAs and GaAs n-i-p-i doping solar cells with ion-implanted selective contacts. Multiple layers of alternate doping are grown by molecular beam epitaxy to form the n-i-p-i structure. After growth, vertical selective contacts are fabricated by Mg and Si ion implantation, followed by rapid thermal annealing treatment and fabrication into circular mesa cells. As means of characterisation, spectral response and illuminated current–voltage (I-V) were measured on the samples. The spectral response suggests that all horizontal layers are able to contribute to the photocurrent. Performance of the devices is discussed with interest in the n-i-p-i structure as a possible design for the GaInP/GaAs/GaInNAs tandem solar cell.</jats:p
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