After over two decades of exploration, tunable diode lasers are beginning to find significant applications, driven largely by the huge demand for bandwidth that is guiding many developments in the optical fiber communication business today. In the paper, some of the history and key developments that have led to the technologies available today are reviewed from the perspective of the author. After discussion of some of the early work, the focus shifts to widely tunable diode lasers, which would appear to be key enablers for future dense wavelength-division multiplexing and optical switching and networking systems. The distinguishing characteristics of the current technological alternatives are summarized.

Monolithic tunable diode lasers

A broad tuning range is demonstrated in tunable DBR lasers with a novel superstructure grating (SSG). These SSG reflectors were fabricated by electron-beam lithography, and grating performance was evaluated by measuring the transmittance characteristics of a ridge-type SSG reflector. Incorporating this SSG reflector into distributed-Bragg-reflector (DBR) laser results in lasers that can be tuned over a wide wavelength range by using coarse and fine tuning mechanisms. Wavelength-tunable SSG DBR lasers were fabricated and operated under low-threshold CW conditions. Wavelength tuning ranges of 50 and 100 nm were designed and experimentally measured to be 50 and 83 nm, respectively, with single-mode operation. >

Broad-range wavelength-tunable superstructure grating (SSG) DBR lasers

Recent progress in the dynamic single-mode (DSM) semiconductor lasers in the wavelength of 1.5-1.6\mu m are reviewed and the basic principle of DSM operation is given. Study of the DSM laser is originated for application to the wide-band optical-fiber communication in the lowest loss wavelength region of 1.5 to 1.65 μm. A DSM laser consists of a mode-selective resonator and a transverse-mode-controlled waveguide, such as the narrow-striped distributed-Bragg-reflector (DBR) laser, so as to maintain a fixed axial mode under the rapid direct modulation. The technology of monolithic integration for optical circuits is applied to realize some of DSM lasers. Structures, static and dynamic characteristics of lasing wavelength, output power, and reliability of the art DSM lasers are reviewed. The dynamic Spectral width of 0.3 nm, the output power of a few milliwatts, and the reliability over a few thousand hours are reported for experimental DSM lasers.

Dynamic single-mode semiconductor lasers with a distributed reflector

Key advances which enabled the InP photonic integrated circuit (PIC) and the subsequent progression of InP PICs to fully integrated multichannel DWDM system-on-chip (SOC) PICs are described. Furthermore, the current state-of-the-art commercial multichannel SOC PICs are reviewed as well as key trends and technologies for the future of InP-based PICs in optical communications.

https://ieeexplore.ieee.org/ielaam/2944/7985001/7954965-aam.pdf

System-on-Chip Photonic Integrated Circuits

The theoretical bases and the experimental results of the dynamic behavior of 1.5-1.6 \mu m GaInAsP/InP dynamic-single-mode (DSM) lasers with distributed Bragg reflector (DBR) are given. A condition for the single-mode operation of a rapidly modulated DBR laser, called a "dynamic-single-mode laser," and the dynamic spectral width were theoretically presented. Experimentally, buried-heterostructure distributed-Bragg-reflector integrated-twin-guide (BH-DBR-ITG) and buried-heterostructure butt-jointed-built-in distributed-Bragg-reflector (BH-BJB-DBR) lasers emitting at the wavelength of 1.5-1.6 \mu m were directly modulated up to 3 GHz, and the stable single-mode operations were obtained in both types of lasers. The dynamic spectral width at the worst modulation condition was measured to be 0.27 nm, which was about \frac{1}{35} times smaller than that of conventional lasers.

1.5-1.6 &#181;m GaInAsP/InP dynamic-single-mode (DSM) lasers with distributed Bragg reflector

A novel GaInAsP/InP integrated laser with butt-jointed built-in distributed-Bragg-reflection waveguide (BJB-DBR integrated laser for short) is proposed and demonstrated. In this structure, it is found theoretically that an efficient coupling of 98% between the active and butt-jointed external waveguides is available by matching the propagation constants and the field profiles of both waveguides, which gives relatively larger fabrication tolerance. Prototype BJB-DBR integrated lasers with emitting wavelength of 1.55 µm were fabricated, and single-longitudinal-mode operation was obtained at room temperature.

GaInAsP/InP integrated laser with butt-jointed built-in distributed-Bragg-reflection waveguide

1.53 μm GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector (BH-DBR-ITG laser) was directly modulated with microwave modulation current superimposed on a DC bias which was fixed at 1.1 times the threshold current, and single-wavelength operation was experimentally confirmed with a modulation frequency up to 1 GHz and a modulation depth of 100%.

Single-wavelength operation of 1.53 μm gainasp/inp buried-heterostructure integrated twin-guide laser with distributed bragg reflector under direct modulation up to 1 ghz

CW operation of a 1.60 μm GaInAsP/InP buried-heterostructure integrated laser with butt-jointed built-in distributed-Bragg-reflection waveguide (BH BJB DBR integrated laser) was achieved at room temperature. Single longitudinal-mode operation at fixed mode was obtained in a temperature range of about 60 deg C, under the CW condition, and it was also maintained under rapid direct modulation of 1.6 GHz.

Room-temperature CW operation of 1.60 μm GaInAsP/InP buried-heterostructure integrated laser with butt-jointed built-in distributed-Bragg-reflection waveguide

A 1.5 ~ 1.6 μm GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector (BH-DBR-ITG laser) was realised, for the first time, and CW operation was achieved up to 255 K. Single-wavelength operation was obtained at temperatures between 228 K and 245 K with the temperature dependence of lasing wavelength of 10 A/deg. At 233 K, the threshold current, the output power and the differential quantum efficiency were 110 mA, 2.2 mW and 4.8%/facet, respectively.

Y. Abe

Papers

GaInAsP/InP integrated laser with butt-jointed built-in distributed-Bragg-reflection waveguide

Single-wavelength operation of 1.53 μm gainasp/inp buried-heterostructure integrated twin-guide laser with distributed bragg reflector under direct modulation up to 1 ghz

Room-temperature CW operation of 1.60 μm GaInAsP/InP buried-heterostructure integrated laser with butt-jointed built-in distributed-Bragg-reflection waveguide

Cw operation of 1.5 ~ 1.6 μm wavelength gainasp/inp buried-heterostructure integrated twin-guide laser with distributed bragg reflector