InGaAsP/InP Laterally Coupled Distributed Feedback Ridge Laser

Abstract

A 1.3-µm-wavelength InGaAsP/InP laterally coupled distributed feedback ridge laser with improved structure and characteristics is reported in this paper. For easier fabrication of the first order grating with 198 nm period on and beside the ridge waveguide side-walls, two-step etching has been used to form a narrow ridge waveguide with a special shape. The grating is patterned by electron beam lithography and deeply transferred also by two-step etching, in order to enhance the lateral evanescent field coupling. A stable CW laser oscillation with a low threshold current of 17 mA at room temperature and a high side mode suppression ratio of 45 dB for a laterally coupled distributed feedback ridge laser has been achieved. An external slope efficiency of 0.25 W/A and an output power of about 25 mW are also available in our most recent devices with anti-reflection and high reflection facet coatings. The optical transmission of a Gbit/s order modulated signal has also been tested using our preliminary laser modules through a 1 km optical fiber.

Laterally coupled distributed feedback lasers emitting at 2 μm with quantum dash active region and high-duty-cycle etched semiconductor gratings

“…In their early demonstrations, such lasers utilizing lateral feedback, have been referred to as corrugated ridge waveguide (CRW) or as laterally coupled distributed feedback (LC-DFB) lasers and included variations in which the grating was etched on the ridge, 18 exclusively in the ridge sidewalls (CRW), 19 exclusively beside the ridge (LC-DFB), 20 or over both regions. 21 More recently, LC-DFB lasers using metallic gratings have also been given particular attention and subsequently used in the industrial applications, as a result of their higher coupling coefficient-induced by the additional periodic loss of the periodic metallic structures, making these lasers mainly gain (loss)-coupled DFB lasers. [22][23][24][25] In additional recent work, improvements in low-loss, high-power operation have been achieved by etched lateral grating fabrication, 13 or by use of a twostep ridge etch process for minimal lateral current spreading.…”

Regrowth-free single-mode semiconductor laser suitable for monolithic integration based on pits mirror

“…Thus, surface-grating distributed Bragg reflector (DBR) lasers and laterally coupled DFB lasers fabricated using only a single epitaxial growth step have received considerable attention. [1][2][3][4][5][6][7][8] However, they still require high-resolution lithography, such as electron beam (e-beam) or high-resolution holographic lithography, which adds to both process time and fabrication expense.…”

Effects of grating order and tooth rounding in laterally coupled distributed feedback lasers

“…To achieve good DFB laser performance, the gratings must be smooth, vertical, and have small periods (e.g., ∼200 nm for a 1st order grating at a wavelength of 1,310 nm). These stringent requirements have made electron-beam lithography the technique of choice thus far for LC-DFB laser fabrication (Chen et al 2000;Muller et al 2002;Das et al 2004;Pozzi et al 2006). E-beam lithography, however, is a serial-write technique that will have a lower manufacturing throughput than parallel-write techniques such as optical lithography.…”