Tunable semiconductor lasers have been listed in numerous critical technology lists for future optical communication and sensing systems. This paper summarizes a tutorial that was given at OFC '03. It includes some discussion of why tunable lasers might be beneficial, an outline of basic tuning mechanisms, some examples of tunable lasers that have been commercialized, and a discussion of control techniques. More extensive data is given for the widely-tunable sampled-grating distributed-Bragg-reflector (SGDBR) type of laser, including data for such lasers integrated monolithically with modulators to form complete transmitter front ends. A summary of reliability data for the SGDBR laser is also given. It is concluded that tunable lasers can reduce operational costs, that full-band tunability is desirable for many applications, that monolithic integration offers the most potential for reducing size, weight, power and cost, and that sufficient reliability for system insertion has been demonstrated.

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Tunable semiconductor lasers: a tutorial

By doping an organic compound functioning as an electron donor (hereinafter referred to as donor molecules) into an organic compound layer contacting a cathode, donor levels can be formed between respective LUMO (lowest unoccupied molecular orbital) levels between the cathode and the organic compound layer, and therefore electrons can be injected from the cathode, and transmission of the injected electrons can be performed with good efficiency. Further, there are no problems such as excessive energy loss, deterioration of the organic compound layer itself, and the like accompanying electron movement, and therefore an increase in the electron injecting characteristics and a decrease in the driver voltage can both be achieved without depending on the work function of the cathode material.

Light Emitting Device

Tunable lasers have been the subject of considerable interest ever since the start of the wavelength division multiplexing (WDM) revolution. In this paper, we bring together views on tunable lasers from different types of companies in the value chain, from operators to laser manufacturers. The purpose of the paper is to give an overview of the state of the art in both deployment and development, as well as to try to predict trends over the coming years.

Tunable lasers in optical networks

Liquid crystals are nowadays widely used in all types of display applications. However their unique electro-optic properties also make them a suitable material for nondisplay applications. We will focus on the use of liquid crystals in different photonic components: optical filters and switches, beam-steering devices, spatial light modulators, integrated devices based on optical waveguiding, lasers, and optical nonlinear components. Both the basic operating principles as well as the recent state-of-the art are discussed.

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Liquid-crystal photonic applications

A complete model with the spin-orbit coupling for strained quantum-well lasers is presented. Explicit formulas for the momentum-matrix elements are given. The improvement in the threshold current density of tensile strained quantum-well lasers, as compared with that of the unstrained quantum well, is shown to result from the enhanced momentum matrix. The differential gain and the linewidth enhancement factor are calculated. The theoretical results show a smaller linewidth enhancement factor for compressively and tensile strained quantum wells than that of the unstrained structure, as has been experimentally observed. The temperature behavior of both the radiative component and the Anger component of the threshold current density is shown. Due to a decrease of gain and differential gain with increasing temperature, the threshold carrier density in unstrained quantum wells is increased with a large increment of the Auger recombination current at high temperature. For strained quantum wells, this increment is moderate because of the smaller threshold carrier density. >

Modeling of strained quantum-well lasers with spin-orbit coupling

A compact full C-band external cavity wavelength tunable laser is proposed. The cavity contains a fixed etalon and makes use of a liquid-crystal-based tunable mirror. The measurement results show a tuning range of 35 nm with fiber coupled power of more than 15 dBm. The sidemode suppression ratio is higher than 50 dB over the whole range and the relative intensity noise is below -148 dB/Hz. The linewidth is in worst case 700 kHz.

Full C-band external cavity wavelength tunable laser using a liquid-Crystal-based tunable mirror

We report on the first demonstrated near-complete coverage of the S-, C-, and L-bands using six different ranges of wavelength-selectable microarray light sources (WSLs) based on a distributed-feedback (DFB) laser diode (LD) array. The six devices were fabricated on only two wafers. Each device has a tuning range of more than 15 nm, a sidemode suppression ratio of over 40 dB, and a fiber-coupled power greater than around 10 mW.

Wavelength-selectable microarray light sources for S-, C-, and L-band WDM systems

Here we propose novel active multi-mode-interferometer (MMI) laser diodes (LDs) for 14XXnm fiber amplifier pump applications. The waveguide of the LDs is consisted from 1x1-MMI couplers integrated with 1st order-mode permitted waveguides to enhance the total active area. Although there is no single-mode waveguide region inside the cavity, the novel active MMI-LDs emitted in stable single-transverse-mode output up to maximum output power. Moreover, they achieved high output power of 1.46W, and low driving voltage of only 1.75V at 1W output power.

First demonstration of novel active multi-mode interferometer (MMI) LDs integrated with 1st order-mode permitted waveguides

MBE growth of ZnCdSe and MgZnCdSe alloys on InP substrates with a GaInAs buffer-layer

Active multi-mode interferometer laser diodes (LDs), implemented in InGaAsP/InP, achieved a significant reduction of 40% (at 0.4 W output) in electric power consumption compared to regular single lobe LDs. With them, a high output power of 0.7 W was also obtained at 14XX nm.

Koichi Naniwae

Papers

Full C-band external cavity wavelength tunable laser using a liquid-Crystal-based tunable mirror

Wavelength-selectable microarray light sources for S-, C-, and L-band WDM systems

First demonstration of novel active multi-mode interferometer (MMI) LDs integrated with 1st order-mode permitted waveguides

MBE growth of ZnCdSe and MgZnCdSe alloys on InP substrates with a GaInAs buffer-layer

High power with low electric power consumption active multi-mode-interferometer laser diode for fibre-amplifier