Growth of a periodic InP-based heteroepitaxial structure for a quantum cascade laser

The route to grow InP-based heteroepitaxial structure for quantum cascade laser by molecular beam epitaxy is reported. Optimized growth conditions including substrate temperature, V/III ratio, growth rates, doping levels and interface control are summarized. Double crystal Xray diffraction and cross-sectional transmission electron microscopy disclose that our grown InP-based heteroepitaxial structure for quantum cascade laser has excellent periodicity and sharp interfaces. (C) 2005 Elsevier B.V. All rights reserved.

Electron beam and laser testing on the novel stripixel detectors

The novel Si stripixel detector, developed at BNL (Brookhaven National Laboratory), has been applied in the development of a prototype Si strip detector system for the PHENIX Upgrade at RHIC. The Si stripixel detector can generate X-Y two-dimensional (2D) position sensitivity with single-sided processing and readout. Test stripixel detectors with pitches of 85 and 560 mu m have been subjected to the electron beam test in a SEM set-up, and to the laser beam test in a lab test fixture with an X-Y-Z table for laser scanning. Test results have shown that the X and Y strips are well isolated from each other, and 2D position sensitivity has been well demonstrated in the novel stripixel detectors. (c) 2005 Elsevier B.V. All rights reserved.

Lowered laser threshold in photonic crystals investigated by semiclassical theory

Using the response formula of the photonic crystals and the Bloch equations, the lasing threshold in arbitrary 2D photonic crystals was obtained by an investigation of steady-state laser behavior. The lasing threshold is expressed by the population inversion. It shows that the population inversion threshold is proportional to the second order of the group velocity, and to the relaxation coefficient. (c) 2004 Elsevier B.V. All rights reserved.

Passive mode locking of diode-end-pumped Nd : GdVO4 laser with an In0.25Ga0.75As output coupler

Passive mode locking of a diode-pumped Nd:GdVO4 laser was demonstrated using In0.25Ga0.75As as saturable absorber as well as output coupler. The pulse width was measured to be about 16 ps with a repetition rate of 146 MHz. The average output power was 120 mW with pump power of 6 W. To our knowledge, this is the first demonstration on a passively mode-locked Nd:GdVO4 laser by using an In0.25Ga0.75As output coupler. (C) 2004 Elsevier B.V. All rights reserved.

Butt-coupled MOVPE growth for high-performance electro-absorption modulator integrated with a DFB laser

A novel butt-joint coupling scheme is proposed to improve the coupling efficiency for the integration of a GalnAsP MQW distributed feedback (DFB) laser with an MQW electro-absorption modulator (EAM). The proposed method gives more than 90% coupling efficiency, being much higher than the 26% coupling efficiency of the common MQW-MQW coupling technique. The differential quantum efficiency of the MQW-bulk-MQW coupled device is also much higher than that of the MQW-MQW device, 0.106 mW/mA versus 0.02 mW/mA. The EAM-DFB devices fabricated by the proposed method exhibit a very high modulation efficiency (12 dB/V) from 0 to I V. By adopting a high-mesa ridge waveguide and buried polyimide, the capacitance of the modulator is reduced to about 0.28 pF. The experimental results demonstrate that the method can replace the conventional MQW-MQW coupling technique to fabricate high-quality integrated photonic devices. (C) 2007 Elsevier B.V. All rights reserved.

High average power and short pulse duration continuous wave mode-locked Nd : GdVO4 laser with a semiconductor absorber mirror

Passive mode locking of a solid-state Nd:GdVO4 laser is demonstrated. The laser is mode locked by use of a semiconductor absorber mirror (SAM). A low Nd3+ doped Nd:GdVO4 crystal is used to mitigate the thermal lens effect of the laser crystal at a high pump power. The maximum average output power is up to 6.5 W, and the pulse duration is as short as 6.2 ps. The optic-to-optic conversion efficiency is 32.5% and the repetition rate is about 110 MHz.

1.3 mu m gain coupled DFB laser with InGaAlAs MQW grown on absorptive InGaAsP corrugation

An InGaA1As multiquantum well (MQW) has been successfully overgrown on the absorptive InGaAsP corrugation for fabricating the 1.3 mu m gain coupled distributed feedback (DFB) lasers. The absorptive InGaAsP corrugation was efficaciously preserved during the overgrowth of the InGaA1As MQW active region. The absorptive InGaAsP corrugation has a relatively high intensity around the PL peak wavelength in comparison with that of the InGaA1As MQW. The fabricated DFB laser exhibited a side mode suppression ratio of 40 dB together with a high single-mode yield of 90%.

Structural and optical properties of ZnO thin films on glass substrate grown by laser-ablating Zn target in oxygen atmosphere

C-axis-orientated ZnO thin films were prepared on glass substrates by pulsed-laser deposition (PLD) technique in an oxygen-reactive atmosphere, using a metallic Zn target. The effects of growth condition such as laser energy and substrate temperature on the structural and optical properties of ZnO films had been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission spectra and room-temperature (RT) photoluminescence (PL) measurements. The results showed that the thickness, crystallite size, and compactness of ZnO films increased with the laser energy and substrate temperature. Both the absorption edges and the UV emission peaks of the films exhibited redshift, and UV emission intensity gradually increased as the laser energy and substrate temperature increased. From these results, it was concluded that crystalline quality of ZnO films was improved with increasing laser energy and substrate temperature. (c) 2007 Elsevier B.N. All rights reserved.

Surface plasmon modulated nano-aperture vertical-cavity surface-emitting laser

We have fabricated surface plasmon modulated nano-aperture vertical-cavity surface-emitting lasers (VCSELs) from common 850 nm VCSELs using focus ion beam etching with Ga+ ion source. The far-field output power is about 0.3 mW at a driving current of 15 mA with a sub-wavelength aperture surrounded by concentric periodic grooves. The enhancement of transmission intensity can be explained by diffraction and enhanced fields associated with surface plasmon. This structure also exhibits beaming properties.

Simultaneous Q switching and mode locking with narrow envelope width in a microchip Nd : YVO4 laser with a composite semiconductor absorber

By using a composite semiconductor absorber and an output coupler, we demonstrated a Q-switched and mode-locked diode-pumped microchip Nd:YVO4 laser. With a 350-mu m-thick crystal, the width of the Q-switched envelope was as short as 12 ns; the repetition rate of the mode-locked pulses inside the Q-switched pulse was more than 10 GHz. The average output power was 335 mW at a maximum pump power of 1.6 W. Q-switched envelope widths of 21 and 31 ns were also achieved with crystals 0.7 and 1.0 mm thick, respectively.

Design and characteristics of quantum cascade laser-based CO detection system

National High Technology Research and Development Program of China 2007AA03Z112；Program of Ministry of Education of China 20060183030；Program of Jilin Provincial Science and Technology Department of China 20070709；Program of Bureau of Science and Technology of Changchun City 2007107

GaN-based violet laser diodes grown on free-standing GaN substrate

National Natural Science Foundation of China 60506001 60776047 60476021 60576003 60836003；National Basic Research Programme of China 2007CB936700

ZnO thin films on Si(111) grown by pulsed laser deposition from metallic Zn target

ZnO thin films with highly c-axis orientation have been fabricated on p-type Si(1 1 1) substrates at 400 degrees C by pulsed laser deposition (PLD) from a metallic Zn target with oxygen pressures between 0.1 and 0.7 mbar. Experimental results indicate that the films deposited at 0.3 and 0.5 mbar have better crystalline and optical quality and flatter surfaces than the films prepared at other pressures. The full width at half maximum (FWHM) of (0 0 0 2) diffraction peak decreases remarkably from 0.46 to 0.19 degrees with increasing annealing temperature for the film prepared at 0.3 mbar. In photoluminescence (PL) spectra at room temperature, the annealed film at 700 degrees C exhibits a smaller ultraviolet (UV) peak FWHM of 108 meV than the as-grown film (119 meV). However, an enhanced deep-level emission is observed. Possible origins to above results are discussed. (c) 2006 Elsevier B.V. All rights reserved.

Dipole mode photonic crystal point defect laser on InGaAsP/InP

In this paper, we focus on the dipole mode of the two-dimensional (2D) photonic crystal (PC) single point defect cavity (SPDC) lasers and we report the fabrication and characterization of 2D PC SPDC lasers with the structure of adjusted innermost air holes. The photonic band and cavity Q factors are simulated by means of plane wave expansion (PWE) and finite-difference time-domain (FDTD), respectively. In order to improve the optical confinement of the SPDC, the diameter of the innermost holes was adjusted. Different lasing performances are observed experimentally. The experimental results agree with the theoretical prediction very well. (c) 2006 Elsevier B.V. All rights reserved.

Room-temperature continuous-wave operation of InAs quantum-wire laser on InP(001) substrate

A self-assembled quantum-wire laser structure was grown by solid-source molecular beam epitaxy in an InAlGaAs-InAlAs matrix oil InP(001) substrate. Ridge-waveguide lasers were fabricated and demonstrated to operate at a heatsink temperature tip to 330 K in continuous-wave (CW) mode. The emission wavelength of the lasers with 5 mm-long cavity was 1.713 mu m at room temperature in CW mode. The temperature stability of the devices was analysed and the characteristic temperature was found to be 47 K in the mnge of 220-320 K.