K. G. Ravikumar

Light Emission from Quantum-Box Structure by Current Injection

Light emitting from quantum-box structure by current injection was observed for the first time. GaInAsP/InP quantum-box structures were fabricated from one-dimensional quantum-well (quantum-film) structures grown by OMVPE. Holographic lithography, wet etching, and LPE regrowth techniques were employed. Three-dimensional quantum size effect was suggested by the wavelength shift of the light emission.

Analysis of electric field effect in quantum box structure and its application to low-loss intersectional type optical switch

The electric field induced refractive-index variation and the refractive-index variation-absorption loss variation ratio in a GaInAs/InP quantum box (QB) structure are analyzed and applied to an intersectional type optical switch. The large index variation of a few percent with low absorption characteristics in a QB structure, is found to be very useful to decrease the insertion loss at both the ON and OFF state of a QB intersectional-type optical switch. It is shown that in such a switch the loss can be decreased to less than 1 dB. The QB size dependence and fluctuations in QB size on QB-intersectional type optical switch are also discussed. >

Switching operation in OMVPE grown GaInAs/InP MQW intersectional optical switch structures

An intersectional optical switch structure with an intersecting angle of 6 degrees was fabricated on an organometallic vapor-phase epitaxy (OMVPE) grown GaInAs/InP multiple quantum-well (MQW) layered wafer. Switching operation using field-induced refractive index variation was successfully demonstrated at the reverse bias voltage of 8 V for the 1.6 mu m wavelength region. Based on this switching, the field-induced refractive index variation in the QW was estimated as around 1%.<<ETX>>

Low-Damage GaInAs(P)/InP Nanometer Structure by Low-Pressure ECR-RIBE

Low defect nanometer structures of 70 nm ~25 nm width are formed in GaInAs/GaInAsP/InP multi-quantum-well layers with low ion extraction voltage (20 V) and at low-pressure (LP) of etching gas (5×10-6 Torr) using electron cyclotron resonance reactive ion beam etching (ECR-RIBE) system for the first time. The room temperature photoluminescence peak intensity after etching and slight cleaning, taking into account the remaining volume of the GaInAs/GaInAsP layer, was almost 60% of that before etching, which proved the very low-damage nature of the present etching method. Moreover we also report for the first time the fabrication of multi-layered GaInAs/InP quantum wire (3 periods) structure using LP-ECR-RIBE.

Field-induced refractive index variation spectrum in a GaInAs/InP quantum wire structure

We report the electric field induced refractive index variation spectrum in a GaInAs/InP multilayered (three layers) quantum wire structure (λg∼1.48 μm) in the range 1.484–1.65 μm with the maximum positive index variation of 4% at around 1.52 μm at an applied reverse bias voltage of 3 V. We have also observed the anisotropic property of the index variation with respect to the quantum wire direction to the input light. These multilayered quantum wire structures were fabricated by low‐pressure electron cyclotron resonance reactive ion beam etching and low‐pressure organometallic vapor phase epitaxy methods.

Electric field-induced absorption in GaInAsP/InP MQW structures grown by LPE

The absorption spectrum induced by applying an electric field was measured for GaInAsP/InP MQW structures with the corresponding bandgap wavelength λg~1.3 µm. A 25-pairs MQW wafer was grown by LPE technique with a well width Lz=150 A, and a barrier width Lb=200 A. The maximum electro-absorption in this waveguide structure was observed to be 550 cm-1 at an applied voltage of 25 V. From this value, the refractive index variation in the quantum well layer was estimated as 0.27%.

Electric-Field-Induced Refractive Index Change In Gainasp/Inp Mqw Structures

Large change in the field induced refractive index is achievable by the use of the MQW structures. The property of which can be advantageously utilized to realize high speed external modulators and switches. The GalnAsP/InP MQW structures was prepared by LPE method and the electric field induced absorption was measured. Reflection of light due to refractive index change as well as absorption coefficient change was observed for the first time. Intersectional optical switch based on this change was also fabricated.

Electric Field Induced Reflection in GaInAsP/InP MQW Structure

Reflection of light due to the electric field effect was seen for the first time in GaInAsP/InP MQW structures through the observation of an interference pattern between the transmitted and reflected light; this was caused by a change in the refractive index and absorption coefficient in the MQW layers due to the partial application of an electric field to the MQW layers. The observed data were fitted with the theoretical simulations and the refractive index change was predicted to be about 0.025% at -5 V. This is a promising step towards the realization of the intersectional optical switch.