Kai-Jun Che

AlGaInAs–InP Microcylinder Lasers Connected With an Output Waveguide

AlGaInAs-InP microcylinder lasers connected with an output waveguide are fabricated by planar technology. Room-temperature continuous-wave operation with a threshold current of 8 mA is realized for a microcylinder laser with the radius of 10 μm and the output waveguide width of 2 μm. The mode Q-factor of 1.2 x 104 is measured from the laser spectrum at the threshold. Coupled mode characteristics are analyzed by 2-D finite-difference time-domain simulation and the analytical solution of whispering-gallery modes. The calculated mode Q-factors of coupled modes are in the same order as the measured value.

Multimode resonances in metallically confined square-resonator microlasers

Directional emission InP/AlGaInAs square-resonator microlasers with a side length of 20 mu m are fabricated by standard photolithography and inductively coupled-plasma etching technique. Multimode resonances with about seven distinct mode peaks in a free-spectral range are observed from 1460 to 1560 nm with the free-spectral range of 12.1 nm near the wavelength of 1510 nm, and the mode refractive index versus the photon energy E (eV) as 3.07152+0.18304E are obtained by fitting the laser spectra with an analytical mode wavelength formula derived by light ray method. In addition, mode field pattern is simulated for cold cavity by two dimensional finite-difference time-domain technique.

InGaAsP–InP Square Microlasers With a Vertex Output Waveguide

InGaAsP-InP square microlasers with a vertex output waveguide are fabricated by planar processes, and the etched sidewalls of the lasers are confined by insulating layer SiO2 and p-electrode Ti-Au metals. For a square microlaser with a side length of 30 μm and a 2-μm -wide output waveguide, a continuous-wave threshold current is 26 mA at room temperature and output power is 0.72 mW at 86 mA. The mode interval of 21 and 7.4 nm is observed for the microlasers with the side length of 10 and 30 μm , respectively. Finite-difference time-domain (FDTD) simulations indicate that the lasing modes have incident angles of about 45 ° at the boundaries of the resonator. In addition, square resonators surrounded by air, SiO2-Ti-Au, and SiO2-Au are compared by FDTD simulations.

Equilateral-Triangle and Square Resonator Semiconductor Microlasers

The characteristics of equilateral-triangle resonator (ETR) and square resonator microlasers are reported, which are potential light sources in the photonic integrations. Based on the numerical simulations, we find that high-efficiency directional emission can be achieved for the triangle and square microlasers by directly connecting an output waveguide to the resonators. The electrically injected InP/InGaAsP ETR and square resonator microlasers with a 2-mum-wide output waveguide were fabricated by standard photolithography and inductively coupled plasma etching techniques. Room-temperature continuous-wave (CW) operations were achieved for the ETR microlasers with the side length from 10 to 30 mum and the square resonator microlasers with the side length of 20 mum. The output power versus CW injection current and the laser spectra are presented for an ETR microlaser up to 310 K and a square resonator microlaser to 305 K. The lasing spectra with mode wavelength intervals as that of whispering-gallery-type modes and Fabry-Parot modes are observed for two square lasers, which can lase at low temperature and room temperature, respectively.

Mode Characteristics for Square Resonators With a Metal Confinement Layer

Microsquare resonators laterally confined by SiO2/Au/air multilayer structure are investigated by light ray method with reflection phase-shift of the multiple layers and two-dimensional (2-D) finite-difference time-domain (FDTD) technique. The reflectivity and phase shift of the mode light ray on the sides of the square resonator with the semiconductor/SiO2/Au/air multilayer structure are calculated for TE and TM modes by transfer matrix method. Based on the reflection phase shift and the reflectivity, the mode wavelength and Q factor are calculated by the resonant condition and the mirror loss, which are in agreement well with that obtained by the FDTD simulation. We find that the mode Q factor increases greatly with the increase of the SiO2 layer thickness d , especially as d < 0.3 ¿m . For the square resonator with side length 2 ¿m and refractive index 3.2, anticrossing mode couplings are found for confined TE modes at wavelength about 1.6 ¿m at d = 0.11 ¿m, and confined TM modes at d = 0.71 ¿m, respectively.

Investigation on multiple-port microcylinder lasers based on coupled modes

Microcylinder resonators with multiple ports connected to waveguides are investigated by 2D finite-difference time-domain (FDTD) simulation for realizing microlasers with multiple outputs. For a 10 μm radius microcylinder with a refractive index of 3.2 and three 2 μ mw ide waveguides, confined mode at the wavelength of 1542.3 nm can have a mode Q factor of 6.7 × 10 4 and an output coupling efficiency of 0.76. AlGaInAs/InP microcylinder lasers with a radius of 10 μm and a 2 μm wide output waveguide are fabricated by planar processing techniques. Continuous-wave electrically injected operation is realized with a threshold current of 4 mA at room temperature, and the jumps of output power are observed accompanying a lasing mode transformation. (Some figures in this article are in colour only in the electronic version)

Long rectangle resonator 1550 nm AlGaInAs/InP lasers

1550 nm AlGaInAs/InP long rectangle resonator lasers with three sides surrounded by SiO2 and p electrode layers are fabricated by planar technology, and room-temperature continuous-wave lasing is realized for a laser with a length of 53 μm and a width of 2 μm. Multiple peaks with wavelength intervals of Fabry-Perot mode intervals and mode Q factors of about 400 and a lasing mode with a Q factor over 8000 are observed from the lasing spectrum at threshold current. The numerical results of the FDTD simulation indicate that the lasing mode may be a whispering-gallery mode, which is a coupled mode of two high-order transverse modes of the waveguide.

Mode behavior in triangle and square microcavities

Directional emission semiconductor microcavity lasers integrated with semiconductor planar technique are potential light sources for photonic integrated circuits. In this article, we investigate mode characteristics for equilateral triangle and square microcavities for realizing directional emission microcavity lasers. The analytical mode field distributions and mode wavelengths are presented for two-dimensional (2D) triangle and square resonators, and directional emission are simulated by finite-difference time-domain (FDTD) technique. The numerical results of mode Q-factors and output coupling efficiencies for the triangle and square resonators show that high efficiency directional emission microcavity lasers can be realized by directly connected an output waveguide to the resonators, because the mode field patterns are standing distributions in the triangle and square resonator. Laser output spectra of fabricated InGaAsP/InP triangle lasers are compared with the analytical results.

Multiple-port directional emission whispering-gallery mode microlasers

Multiple-port directional emission microlasers are potential light sources and optical signal processing units in photonic integrated circuits. Connecting bus waveguides to a microresonator is a simple method to realize directional emission microlasers. In this paper, we investigate square and circular resonator microlasers connected with multiple bus waveguides. The mode characteristics of the microresonators connected with multiple bus waveguides are simulated by finite-difference time-domain technique, and the numerical results of mode Q factors and output coupling efficiencies show that high efficiency directional emission microresonator lasers can be realized. Furthermore, the microcylinder laser connected with a bus waveguide fabricated by planar technology processes is reported, and the lasing spectra of square microlasers with four vertices connected to bus waveguides are analyzed.

Mode coupling and directional emission in mirocylinder lasers

CW Electrically injected AlGaInAs/InP microcylinder lasers are realized with 10µm radius and a 2µm-wide output waveguide at room temperature. High output efficiency is predicted for coupled microcylinders with an output waveguide by 2D FDTD simulation.