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Distributed feedback lasers with photon-photon-resonance-enhanced modulation bandwidth

Multi-section distributed-feedback lasers with surface gratings have been fabricated without re-growth by employing ultraviolet nanoimprint lithography. High-frequency photon-photon resonance was exploited to extend the direct modulation bandwidth beyond the conventional limits set by the carrier-photon resonance.

Distributed feedback lasers with alternating laterally coupled ridge-waveguide surface gratings

Distributed feedback lasers with laterally coupled ridge-waveguide surface gratings having the protrusions placed alternately on the lateral sides of the ridge are demonstrated. This configuration enables easier-to-fabricate wider trenches than in the gratings with protrusions placed symmetrically on both sides of the ridge. The design strategy and coupling coefficient calculations are discussed. The output characteristics of fabricated lasers show lower threshold currents and higher slope efficiencies for devices with first-order alternating gratings than for those with third-order symmetric gratings having comparable grating trench widths and similar coupling coefficients.

Spectral Characteristics of Narrow-Linewidth High-Power 1180 nm DBR Laser With Surface Gratings

We report narrow-linewidth 1180-nm GaInNAs/GaAs distributed Bragg reflector lasers reaching up to ~500-mW continuous-wave output power at room temperature. The lasers employ surface gratings, which avoided the problematic regrowth and enabled a high side-mode suppression ratio over a relatively large mode-hop-free tuning range. The wavelength tuning rates of 0.1 nm/°C and 1 pm/mA were obtained by changing the mount temperature and the drive current, respectively. The lasers exhibit a narrow emission linewidth (<;250 kHz) even at high output power levels. The side-mode suppression ratio is relatively independent of the power level and remains higher than 50 dB even in the vicinity of the roll-off point. An outstanding temperature stability is provided by good carrier confinement in the GaInNAs/GaAs quantum well. A 2000 h burn-in with constant 1.5 A bias at 20 °C improved the output characteristics slightly and did not reveal any failure among the tested components.

High-Power 1180-nm GaInNAs DBR Laser Diodes

We report high-power 1180-nm GaInNAs distributed Bragg reflector laser diodes with and without a tapered amplifying section. The untapered and tapered components reached room temperature output powers of 655 mW and 4.04 W, respectively. The diodes exhibited narrow linewidth emission with side-mode suppression ratios in the range of 50 dB for a broad range of operating current, extending up to 2 A for the untapered component and 10 A for the tapered component. The high output power is rendered possible by the use of a high quality GaInNAs-based quantum well gain region, which allows for lower strain and better carrier confinement compared with traditional GaInAs quantum wells. The development opens new opportunities for the power scaling of frequency-doubled lasers with emission at yellow–orange wavelengths.

Simulation of photon-photon resonance enhanced direct modulation bandwidth of DFB lasers

Simulations and experimental results of high-frequency photon-photon resonance are used to examine the possibilities to extend the direct modulation bandwidth in dual-mode distributed feedback lasers beyond the conventional limit set by the carrier-photon resonance.

Transverse structure optimization of laterally-coupled ridge waveguide DFB lasers

A new figure of merit for single transverse mode operation and an accurate procedure for calculating the coupling coefficient in distributed feedback lasers with laterally-coupled ridge waveguide surface grating structures are introduced. Based on the difference in optical confinement between the pumped and un-pumped regions in the transverse plane, the single transverse mode figure of merit is effective and easy to calculate, while the improved coupling coefficient calculation procedure gives experimentally confirmed better results than the standard calculation approaches.

Difference frequency modulation of multi-section dual-mode lasers with nanoscale surface gratings

Dual-mode multi-section quantum-well distributed feedback lasers with surface gratings have been fabricated, without regrowth, at 1310 and 1550 nm using UV nano-imprint lithography. Several laser and grating sections have been employed to control and stabilize the dual-mode emission and to reduce mode competition. Frequency differences between 15 GHz and 1 THz were achieved for different longitudinal structures. Frequency difference variations of several GHz have been measured under bias modulation with rates up to a few GHz. Higher frequency difference modulation rates are expected from improved measurement setups and from employing quantum dot active regions for further reduction of mode competition.

Difference Frequency Modulation in Dual-Mode Multi-Section DFB Lasers

Dual-longitudinal-mode multi-section DFB lasers with surface gratings were fabricated at 1310 and 1550 nm. Frequency differences between 15 and 1000 GHz were achieved and were modulated by several GHz with rates up to 10 GHz.

Dual-mode multi-section lasers with nanoscale surface gratings

Dual-mode multi-section distributed-feedback lasers with surface gratings have been fabricated using UV nanoimprint lithography. Frequency differences from 14GHz to 1.3THz for different longitudinal structures and frequency difference modulation speed up to 500MHz have been measured.