Spot-size Converter Integrated Laser Diode Research Articles

Circularly Polarized External Cavity Laser Hybrid Integrated With a Polyimide Quarter-Wave Plate on Planar Lightwave Circuit

We propose and demonstrate a circularly polarized external cavity laser (ECL) hybrid integrated on a planar lightwave circuit (PLC). The ECL is composed of a spot-size converter integrated laser diode, a UV-written grating, and a polyimide quarter-wave plate on the PLC using hybrid-integration technology. The polyimide quarter-wave plate of an 8.8-mum thickness was inserted in a trench with a 20-mum width and a 300-mum depth on the PLC platform, and fixed with a UV-curable adhesive. The ECL hybrid integrated with the polyimide wave plate becomes highly circular-polarized with a degree of circular polarization of 0.992. This circularly polarized ECL operated with a sidemode suppression ratio of >50 dB at ~1550 nm.

1.55-μm spot-size converter integrated laser diode with conventional buried-heterostructure laser process

A 1.55-μm spot-size converter integrated laser diode is demonstrated with conventional buried-heterostructure laser process. For the spot-size converter, we employed a double-waveguide structure in which a ridge-based passive waveguide was incorporated. The passive waveguide was optically combined with a laterally tapered active waveguide to control mode size. The threshold current was measured to be 5 mA together with high slope efficiency of 0.45 W/A. The beam divergence angles in the horizontal and vertical directions were as small as 9.0/spl deg/ and 7.8/spl deg/, respectively.

Hybrid-integrated external-cavity laser without temperature-dependent mode hopping

We propose and demonstrate an integrated external-cavity laser (ECL) with a novel configuration designed to suppress temperature-dependent mode hopping. The laser cavity is composed of a spot-size converter integrated laser diode (SS-LD), a UV-written grating, and silicone-filled grooves on a planar lightwave circuit (PLC). The silicone is used to compensate for the difference between the temperature coefficients of the SS-LD and the silica waveguides. We calculate theoretically the temperature interval of the mode hopping in the ECL to optimize the length of the silicone-filled grooves. We fabricated test and practical lasers with the proposed configuration using PLC hybrid-integration technologies. With the test laser, we confirmed stable single-mode oscillation and a large increase in the mode-hopping temperature interval for both static and dynamic operation. We obtained a low threshold of 15 mA, an optical power of 1.0 mW at 25/spl deg/C, and an injection current of 60 mA. In the practical laser, which we additionally integrated with a front monitor photodiode, we realized auto power control with mode-hopping-free operation from 18/spl deg/C to 56/spl deg/C. These results indicate the good performance levels of our proposed laser.

Highly reliable spot-size converter integrated laser diodes over a wide temperature range for access network systems

In this paper, we present highly reliable high-temperature spot-size converter integrated laser diodes (LDs) fabricated using a full-wafer process with dry etching and MOVPE. The lasers lase at 150°C and operate stably for 10,000 h at 85°C and 10 mW. The median lifetime is estimated to be over 10 5 h. We also demonstrate a novel screening test procedure for a bar configuration of LDs, which can greatly reduce optical module cost.

1.55 ?m spot-size converter integrated-laser diode fabricated by selective-area metalorganic vapor-phase epitaxy

A 1.55 μm spot-size converter integrated-laser diode (SSC–LD) with a vertically tapered-thickness waveguide was fabricated by using selective-area metalorganic vapor-phase epitaxy (MOVPE). A tapered-thickness profile and PL wavelength shift as large as 238 nm in the waveguide were obtained by using an exponentially tapered shape mask. The SSC–LD exhibited a high slope efficiency of 0.31 W/A and a beam divergence of 6.9°×12.4° without facet coating. The coupling loss between the LD and SMF was measured to be 2.76 dB, and the 1 dB alignment tolerances were ±2.4 μm for the horizontal direction, ±2.0 μm for the vertical direction, and 13 μm for the longitudinal direction. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 300–302, 2000.

An inclined coupling between laser and fiber scheme to reduce optical reflection with a spot-size converter integrated laser diode

An inclined coupling between laser and fiber (ICLF) scheme is proposed as a cost-effective means of reducing optical reflection, which causes degradation of the laser diode's relative intensity noise (RIN) characteristic. In wireless systems using sub-carrier optical transmission, it is important to achieve desirable transmission performance with low-cost optical devices to meet system requirements while keeping costs down. Optical reflection caused by optical connectors, however, prevents the attainment of such performance in optical devices. This paper describes the use of ICLF technology to reduce optical reflection. It is shown both theoretically and experimentally that the use of this technology greatly improves both the RIN and the receiver sensitivity. This technology will enable cheaper optical devices implementations in fiber-oriented wireless access systems.

Reliability of 1300-nm spot-size converter integrated laser diodes for low-cost optical modules in access networks

This paper discusses the degradation behaviors and reliability of spot-size converter integrated laser diodes fabricated using the full wafer process with dry etching and metal organic vapor phase epitaxy (MOVPE). Failure criteria applicable to actual access networks were determined based on the degradation behavior exhibited in several aging tests, and device lifetimes were then estimated. The far-field patterns and wide-temperature operation required for low-cost system application scarcely changed during degradation, even after a 150% increase in threshold current. Within this degradation range, the device life for system application is estimated to be more than 10/sup 5/ h at 60/spl deg/C and 10 mW.

Design and fabrication of high-coupling efficiency spot-size converter integrated laser diodes using three-dimensional BMP program

Attention is focused on butt-joint-type spot-size converter integrated laser diodes (SSC-LD's), which allow us to independently optimize the high-temperature performance and coupling efficiency. Increasing the coupling efficiency is achieved by using the three-dimensional (3-D) beam propagation method (BPM). Particular attention is paid to keeping coupling efficiency high, while minimizing variations due to fluctuations in fabrication conditions, such as composition and mesa width. The validity of this method is demonstrated by fabricating a device designed in this way; its coupling efficiency is in excellent agreement with the designed value.

Comparison of coupling characteristics for several spotsize-converter-integrated laser diodes in the 1.3-μm-wavelength region

Four types of spotsize-converter-integrated laser diodes (SS-LDs) are numerically compared from the viewpoint of the coupling characteristics to the single-mode fiber in the 1.3-μm-wavelength region. The comparison is based on the semivectorial three-dimensional (3-D) finite-difference (FD) beam propagation method (BPM). The SS-LDs investigated here are categorized into a group with vertical tapers and a group with a combination of a lateral taper and a thin-film core. The features of the SS-LDs are clarified.

High-coupling efficiency of a 1.3-μm spot-size converter integrated laser diode with pn-buried heterostructure for high-temperature operation

We propose a novel design concept for low-loss coupling with high laser performance in a spot-size converter integrated laser diode (SS-LD) with a pn-buried heterostructure (pn-BH) and demonstrate both the good coupling efficiency and high laser performance. We clarify that a high position and a high doping concentration of an n-InP current blocking layer in the pn-BH are favorable for high-coupling efficiency with a single-mode fiber by a two-dimensional (2-D) finite-element method-based calculation. By using the proposed concept, low-loss coupling of 1.6 dB with a low threshold current of 5.5 mA at room temperature and 19.6 mA even at 85/spl deg/C was achieved experimentally.

Coupling and conversion characteristics of spot-size-converter integrated laser diodes

The coupling and conversion characteristics of four types of spot-size converter integrated laser diodes (SS-LDs) to a single-mode fiber (SMF) in the 1.3-/spl mu/m-wavelength region are numerically clarified. The SS-LDs are categorized into types with vertical tapers and types with a combination of a lateral taper and a thin-film core. The eigenmodes are obtained by the finite-element method (FEM). The semivectorial 3-D finite-difference (FD) beam propagation method (BPM) is used to calculate the propagating beams.

Passively aligned hybrid WDM module integrated withspot-size converter integrated laser diode and waveguide photodiode on PLC platformfor fibre-to-the-home

A low cost and high performance hybrid WDM module assembled by passive alignment has been developed for FTTH systems. High coupling efficiency of a spot-size converter integrated laser diode to a PLC waveguide, which facilitates mass production of the module, is achieved. A minimum optical received power of -37 dBm for a 50 Mbit/s burst signal is also achieved

Design of a spotsize-converter-integrated laser diode (SS-LD) with a lateral taper, thin-film core and ridge in the 1.3-μm-wavelength region based on the 3-D BPM

In order to develop spotsize-converter-integrated laser diodes (SS-LDs) with high efficiency and large-misalignment tolerances in the 13-/spl mu/m-wavelength region, spotsize converters (SSCs), which consist of lateral taper, thin-film core and ridge, are investigated employing the three-dimensional (3-D) semivectorial finite-difference beam propagation method (FD-BPM) with nonequidistant discretization. The sum of the spot-conversion loss and coupling loss between the laser diode (LD) eigenmode and the single-mode fiber (SMF) eigenmode are calculated for various structural parameters. Small loss of around 1.5 dB can be achieved by introducing a nonlinear taper. The fabrication tolerances for the SSCs are also clarified. The calculated results agree well with the results for actually fabricated SS-LD's. It is also shown that the radiation loss and coupling characteristics of the SS-LDs with a buried thin-film core structure can be improved using a nonlinear taper.