Ho Sung Cho

High-Performance Strain-Compensated Multiple Quantum Well Planar Buried Heterostructure Laser Diodes with Low Leakage Current

The dependence of leakage current in a planar buried heterostructure laser diode (PBH-LD) on the operating temperature was analyzed by taking the effects of the connection width between a p-InP clad layer and a p-InP blocking layer into account. A two-step etching process comprising nonselective mesa etching followed by InP selective etching is proposed for obtaining a narrow connection width and high controllability of an active layer width. The performance was compared for LDs fabricated using the two-step etching process and those fabricated using conventional nonselective etching process. The average threshold current and the slope efficiency of the 1.3 µ m strain-compensated multiple quamtum well (MQW) PBH-LD fabricated using the two-step etching process were 5.6 mA and 0.27 mW/mA, respectively, for a cavity length of 400 µ m. However, using the nonselective etching process, the average threshold current was 14.5 mA and the slope efficiency was 0.22 mW/mA, given the same cavity length. A higher differential gain and characteristic temperature were also obtained due to the lower leakage currents and strain-compensated multiple quantum well active layers.

InAsP phase formations during the growth of a GalnAsP/lnP distributed feedback laser diode structure on corrugated lnP using metalorganic vapor phase epitaxy

An InAsP phase formed during the heatup time to the growth temperature of MOVPE was investigated by transmission electron microscopy and energy dispersive spectroscopy. The thickness of the InAsP phase on the concave regions of corrugation is increased with increased AsH3 partial pressure and heat‐up time. The arsenic composition in InAsP was also increased with the increase of AsH3 partial pressure during the heat‐up time. Dislocations and defects were not generated below an AsH3 partial pressure of 2.4×10−3 Torr, although strain was induced according to the thickness and composition of InAsP formed on the concave regions of corrugation.

Mode-locked fiber laser gyroscope based on a distributed-feedback semiconductor laser amplifier.

A mode-locked fiber laser gyroscope is reported that uses a distributed-feedback semiconductor laser amplif ier as the gain medium. Stable mode-locked optical pulses were obtained without gain competition, and the pulse interval could be measured with much-improved accuracy as a function of rotation rate. The rms noise equivalent rotation rate was measured to be 0.4 deg/ radicalh.

HIGH POWER OPERATIONS OF 980 NM GA0.8IN0.2AS/GAXIN1-XASYP1-Y/GA0.51IN0.49P/GAAS PUMP LASERS PREPARED BY MULTI-STEP METALORGANIC VAPOR PHASE EPITAXIAL GROWTH WITH ION IMPLANTED CHANNELS

The silicon (Si) or boron (B) implantation process in Ga0.8In0.2As/GaxIn1-xAsyP1-y/Ga0.51In0.49P/GaAs quantum well structures can be used not only for maintaining single lateral mode during high power operation but also for increasing the catastrophic optical damage (COD) level of 980 nm pump lasers. The fabricated 980 nm pump lasers with partially ion implanted channels after ridge waveguide structure formation exhibited high power operation up to 250 mW without any kink and beam steering. A photoluminescence peak shift of 70 meV was obtained by 120 keV Si-implantation and annealing at 900°C. Improvement of the COD level by a minimum of 1.65 times is obtained by forming transparent windows near facets by Si implantation and annealing. A highly nonradiative polycrystalline phase of the active area may be the major cause of COD failure in the Al-free 980 nm lasers.

Interfacial layer formation on corrugated InP during the epitaxial growth of GaInAsP InP distributed feedback laser diode structure

Abstract The interfacial layer formed during the soaking procedure of liquid phase epitaxy (LPE) growth and the heat-up procedure to the growth temperature of metalorganic vapor phase epitaxy (MOVPE) was investigated by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). A thin interfacial layer between an epitaxially grown GaInAsP layer and the concave region of the corrugated InP grating is formed in LPE growth using a GaAs cover crystal. The thickness of this interfacial InAsP layer in the concave region of corrugation is increased with increased AsH 3 partial pressure and heat-up time in MOVPE. The arsenic composition in the InAsP layer also increased with increased AsH 3 partial pressure. Dislocations and defects were not generated in LPE growth using a GaAs cover crystal and using an AsH 3 over pressure and heat-up procedure to the growth temperature in MOVPE.

Effects of Implanted Materials on Impurity-Induced Layer Disordering in Strained Ga0.8In0.2As/GaxIn1-xAsyP1-y/Ga0.51In0.49P/GaAs Quantum Well Structure

The impurity-induced layer disordering in B- or Si-implanted Ga0.8In0.2As/Gax In1-x Asy P1-y /Ga0.51In0.49P /GaAs quantum well structure has been studied. The wavelength shift of the photoluminescence peak and the degree of intermixing can be determined by the type and energy of implanted ions with followed annealing at the temperature of 900° C. A photoluminescence peak shift of 70 meV was obtained by 120 keV Si-implantation and annealing at 900° C. The diffused interface was also studied by cross sectional transmission electron microscopy.

The structural properties of spot size converted laser diodes fabricated by butt-joint selective area growth

Low cost laser diode modules are crucial issues for optical access network. The narrow beam of the laser diode is inevitable for passive alignment between a laser and a single mode fiber (SMF) or a planar lightwave circuit (PLC) in hybrid integration scheme in the low cost laser module for optical access network. The narrow beam of laser diode can be obtained by spot size converter which increases the mode field diameter using passive waveguide in output facet of laser diodes. The passive waveguides for spot size converter were fabricated by butt-joint selective area growth in order to optimize each region independently.