P.V. Studenkov

Efficient coupling in integrated twin-waveguide lasers using waveguide tapers

We demonstrate a 1.55-/spl mu/m wavelength, InGaAsP-InP, twin-waveguide (TG) laser integrated with passive ridge waveguides using low-loss taper couplers. The lateral taper on the laser waveguide induces efficient resonant coupling of light between the active and passive layers. The device is fabricated using low-cost conventional photolithography and reactive ion etching of a TG structure grown by gas-source molecular beam epitaxy. This structure is suitable for integrating a variety of photonic devices without requiring epitaxial regrowth.

Asymmetric twin-waveguide 1.55-μm wavelength laser with a distributed Bragg reflector

We demonstrate a single frequency, 1.55 /spl mu/m wavelength laser based on an asymmetric twin-waveguide structure using a single growth step and a simple fabrication process. The external Bragg grating is formed on the passive ridge waveguide, optically coupled to the twin-guide gain section using a low loss, tapered mode transformer. The grating is produced by near-field holographic printing using a phase mask. Output powers >11 mW in a small-spot waveguide with a side-mode suppression ratio >40 dB and a slope efficiency of 0.11 W/A are obtained under pulsed operation. These performance characteristics are comparable to conventional, nonintegrated, conventional discrete DBR lasers, although the twin-waveguide design is compatible with photonic integrated circuits such as monolithic transmitters and WDM coherent receivers.

Low-threshold current, high-efficiency 1.3-μm wavelength aluminum-free InGaAsN-based quantum-well lasers

We demonstrate high-performance Al-free InGaAsN-GaAs-InGaP-based long-wavelength quantum-well (QW) lasers grown on GaAs substrates by gas-source molecular beam epitaxy using a RF plasma nitrogen source. Continuous wave (CW) operation of InGaAsN-GaAs QW lasers is demonstrated at /spl lambda/=1.3 /spl mu/m at a threshold current density of only J/sub TH/=1.32 kA/cm/sup 2/. These narrow ridge (W=8.5 /spl mu/m) lasers also exhibit an internal loss of only 3.1 cm/sup -1/ and an internal efficiency of 60%. Also, a characteristic temperature of T/sub 0/=150 K from 10/spl deg/C to 60/spl deg/C was measured, representing a significant improvement over conventional /spl lambda/=1.3 /spl mu/m InGaAsP-InP lasers. Under pulsed operation, a record high maximum operating temperature of 125/spl deg/C and output powers greater than 300 mW (pulsed) and 120 mW (CW) were also achieved.

Monolithic integration of a quantum-well laser and an optical amplifier using an asymmetric twin-waveguide structure

We demonstrate the monolithic integration of a 1.55 /spl mu/m wavelength InGaAsP-InP multiple-quantum-well (MQW) laser and a traveling-wave optical amplifier using an asymmetric, vertical twin-waveguide structure. The laser and amplifier share the same strained InGaAsP MQW active layer grown by gas-source molecular beam epitaxy, while the underlying passive waveguide layer is used for on-chip optical interconnections between the active devices. The asymmetric twin-waveguide structure uses the difference in modal gains to discriminate between the even and odd modes.

Uncooled, 10 Gb/s 1310 nm electroabsorption modulated laser

We demonstrate the first 10 Gb/s, 1310 nm EML operating uncooled from 0-85 /spl deg/C. Transmission over 20 km with zero power penalty and a 26% SONET eye-mask margin after 10 km are reported.

High-performance long-wavelength (/spl lambda//spl sim/1.3 μm) InGaAsPN quantum-well lasers

We demonstrate high-performance InGaAsPN quantum well based long-wavelength lasers grown on GaAs substrates, nitrogen containing lasers emitting in the /spl lambda/=1.2- to 1.3-/spl mu/m wavelength range were grown by gas source molecular beam epitaxy using a RF plasma nitrogen source. Under pulsed excitation, lasers emitting at /spl lambda/=1.295 /spl mu/m exhibited a record low threshold current density (J/sub TH/) of 2. 5 kA/cm/sup 2/. Lasers grown with less nitrogen in the quantum well exhibited significantly lower threshold current densities of J/sub TH/=1.9 kA/cm/sup 2/ at /spl lambda/=1.27 /spl mu/m and J/sub TH/=1.27 kA/cm/sup 2/ at /spl lambda/=1.2 /spl mu/m. We also report a slope efficiency of 0.4 W/A and an output power of 450 mW under pulsed operation for nitrogen containing lasers emitting at 1.2 /spl mu/m.

Design and operation of uncooled 10 Gb/s, 1310 nm electroabsorption modulated lasers

We describe the design and operation of a 10 Gb/s, 1310 nm wavelength, electroabsorption modulated laser (EML) working uncooled between 0-85 /spl deg/C. The limiting nature of the EA modulator transfer curve simplifies RF drive environment, reduces RF testing and enables excellent RF performance in low-cost TO-can based packages. The performance advantage of the EML for 1310 nm short reach links is demonstrated at the die level with SONET eye-margins >20% and extinction ratios >9 dB. We also report for the first time a high performance, SONET compliant TO-can based TOSA using an uncooled EML.

Low-loss, low-threshold 0.98 /spl mu/m wavelength InGaAsP/InGaP/GaAs broadened waveguide lasers grown by GSMBE

We describe the design and experimental results for broadened waveguide (BW) high-power, low-loss, low threshold current 0.98 /spl mu/m-aluminum-free InGaAsP/InGaP/GaAs lasers. The dramatic decrease in the internal losses with an increase in the width of the waveguide layer for a SCH-MQW structure, is attributed to lower free-carrier absorption due to the reduced overlap of the optical mode with the highly doped cladding regions. The BW lasers grown with both InGaAsP and GaAs waveguides show lower internal loss and threshold current than those designed for optimum optical confinement factor within the QW region. We report a record low internal loss of 2.2 cm/sup -1/ and highest CW output power of 6.8 W for a InGaP/GaAs laser grown by GSMBE. We also report the highest quasi-continuous output power of 13.3 W measured for a single 100 /spl mu/m aperture, 0.8-0.98 /spl mu/m Al-free laser diode, grown by either MBE or MOCVD.

Large-scale monolithic integration technologies for InP-based transmitters and receivers

We discuss approaches to achieving large scale InP-based optoelectronic integrated circuits (OEICs) and photonic integrated circuits (PICs). For the last several years, we have developed such platform integration technologies, with a recent success being the demonstration of a 16x16 InGaAs/InP imaging array consisting of 272 field effect transistors and 256 p-i-n detectors. Both growth and processing of the platform structure are simple and robust, allowing for large-scale integration of optical and electronic devices. Other components which have been demonstrated using this versatile receiver/focal plane array technology have been very high sensitivity switched photodiode receivers, and coherent optical receivers. The transmitter technology consists of a modified twin waveguide structure which allows for fault tolerant fabrication of photonic integrated circuits employing any combination of lasers, optical amplifiers, modulators and waveguides. The extremely high yield and simplicity of processing of such InP-based LSI circuits suggests that the scale of optoelectronic integration in this important materials system has reached a new, and highly useful level of sophistication.

Monolithic integration of laser and waveguide using a twin-guide structure with absorption layer

We demonstrate for the first time the use of absorption layer to achieve mode control in an InP/InGaAsP integrated twin-guide (TG) laser structure. The In/sub 0.53/Ga/sub 0.47/As layer eliminates the even mode and makes characteristics of the integrated device insensitive to laser cavity length and structure variations, without degrading performance. A record high coupling efficiency of 45% from the TG laser to the integrated passive waveguide is obtained.