Distributed Feedback Ridge Waveguide Laser Research Articles

Distributed feedback ridge waveguide lasers fabricated by CNP process

In this work, cost efficient hybrid polymer based Bragg grating ridge waveguide resonators were successfully fabricated by a cost-effective combined nanoimprint and photolithography process. By using this hybrid process, optical features with the size in the scale of nanometers (Bragg gratings) and micrometers (waveguides) could be defined simultaneously in one step. The high quality mask-stamp for the CNP process was fabricated by the combination of electron-beam lithography, reactive ion etching and standard lift-off methods on a UV transparent glass wafer. For the following CNP process, the silicon-containing, inorganic-organic hybrid material OrmoCore® was used as the ridge-type waveguide core material due to its high chemical and physical stability as well as its low optical loss in the visible wavelength region. After depositing the active gain material (Alq3:DCM2) on top of the duplicated Bragg grating area, an optically pumped distributed feedback ridge waveguide laser source has been successfully fabricated. The full width at half maximum value of the laser was 180pm and the threshold for laser activity at 652.34nm was about 19μJ/cm2.

Tunable 975 nm nanosecond diode-laser-based master-oscillator power-amplifier system with 163 W peak power and narrow spectral linewidth below 10 pm

A spectrally tunable, narrow linewidth master oscillator power amplifier system emitting ns pulses with high peak power is presented. The master oscillator is a distributed feedback ridge waveguide (DFB-RW) laser, which is operated in continuous wave (CW) mode and emits at about 975 nm with a spectral line width below 10 pm. The oscillator can be tuned over a range of 0.9 nm by varying the injection current. The tapered amplifier (TA) consists of an RW section and a flared gain-guided section. The RW section of the amplifier acts as an optical gate and converts the CW input beam emitted by the DFB-RW laser into a train of short optical pulses, which are subsequently amplified by the tapered section. The width of the pulses is 8 ns at a repetition rate of 25 kHz. The peak power is 16.3 W. The TA preserves the spectral properties of the emission of the DBR-RW laser. The amplified spontaneous emission is suppressed by about 40 dB.

Laterally‐coupled distributed feedback laser with first‐order gratings by interference lithography

The first laterally-coupled distributed feedback (DFB) laser with first-order sidewall gratings fabricated by optical interference lithography is experimentally demonstrated. The gratings were first etched into a dielectric mask on the planar top surface of an InP/AlGaInAs laser epiwafer, and then transferred to both sidewalls of a 2 µm deep ridge-waveguide structure using a novel self-aligned process. DFB ridge-waveguide lasers with a cavity length of 650 µm and width of 2.6 µm (with 300 nm gratings on both sidewalls) achieved single longitudinal mode continuous-wave operation, with a sidemode suppression ratio of 37 dB. The threshold current density is 1.7 kA/cm2 at room temperature, and the slope efficiency is 0.14 mW/mA per facet (uncoated).

Dynamics of a gain-switched distributed feedback ridge waveguide laser in nanoseconds time scale under very high current injection conditions

We present detailed experimental investigations of the temporal, spectral and spatial behavior of a gain-switched distributed feedback (DFB) laser emitting at a wavelength of 1064 nm. Gain-switching is achieved by injecting nearly rectangular shaped current pulses having a length of 50 ns and a very high amplitude up to 2.5 A. The repetition frequency is 200 kHz. The laser has a ridge waveguide (RW) for lateral waveguiding with a ridge width of 3 µm and a cavity length of 1.5 mm. Time resolved investigations show, depending on the amplitude of the current pulses, that the optical power exhibits different types of oscillatory behavior during the pulses, accompanied by changes in the lateral near field intensity profiles and optical spectra. Three different types of instabilities can be distinguished: mode beating with frequencies between 25 GHz and 30 GHz, switching between different lateral intensity profiles with a frequency of 0.4 GHz and self-sustained oscillations with a frequency of 4 GHz. The investigations are of great relevance for the utilization of gain-switched DFB-RW lasers as seed lasers for fiber laser systems and in other applications, which require a high optical power.

Picosecond Spectral Dynamics of Gain-Switched DFB Lasers

We study the generation of picosecond pulses by gain-switching of distributed feedback ridge-waveguide laser diodes. By pumping with short current pulses without d.c. bias, we obtain laser pulses with peak powers above 1 W at a wavelength around 1065 nm. These pulses exhibit strong spectral dynamics stemming from mode competition after switch-on. Typically, emission begins with a broad spectrum, before narrowing down to the Bragg line within a few hundred picoseconds. This dynamic behavior is studied in detail both experimentally and numerically for a variety of grating parameters. Using a rate-equation model with two species of photons, we achieve excellent agreement between simulation and experiment. In conclusion, we discuss the optimization of DFB laser diodes for short pulse generation.

High peak-power nanosecond pulses generated with DFB RW laser

The generation of optical pulses with very high-peak power by gain-switching of a distributed-feedback (DFB) ridge-waveguide (RW) laser emitting at a wavelength of 1064 nm is demonstrated. With 4 ns-long pulses a peak power of 2.6 W is achieved at a repetition frequency of 250 kHz. The rise and fall times of the pulses are about 1.2 ns. The spectral full width at half maximum ranges between 30 and 40 pm for all powers, whereas the width enclosing 95% of the intensity increases from 90 to 450 pm from low to high power. The laser has a cavity length of 1 mm.

40-Gb/s Direct Modulation With High Extinction Ratio Operation of 1.3-$\mu$m InGaAlAs Multiquantum Well Ridge Waveguide Distributed Feedback Lasers

Direct modulation at 40 Gb/s of a 1.3-mum InGaAlAs distributed feedback ridge waveguide laser is experimentally demonstrated. By combination of the high differential gain of an InGaAlAs multiquantum well active layer, a short cavity length of 100 mum, and a low-resistance notch-free grating, it achieves high bandwidth of 29 GHz and high-extinction ratio of 5 dB at 40-Gb/s modulation. Moreover, the laser operates at a record maximum ambient temperature of 60degC under 40-Gb/s directly modulation. It also achieves 40-Gb/s modulated transmission over 2 km with a low power penalty of 0.25 dB at 25degC .

Distributed feedback ridge waveguide lasers fabricated by nanoscale printing and molding on nonplanar substrates

This letter describes the use of printing and molding techniques to fabricate plastic photopumped laser that use distributed feedback resonators on ridge waveguides. The results indicate (i) potential optoelectronic applications of a set of emerging low cost lithographic techniques that can pattern a range of materials with submicron resolution on nonplanar substrates, (ii) a new type of plastic laser based on molded organic gain materials, and (iii) that thresholds of plastic distributed feedback ridge waveguide lasers are similar to their planar counterparts.

Continuous-wave operation of 1.5 μm distributed-feedback ridge-waveguide lasers

CW operation of 1.5 μm ridge-waveguide DFB lasers is reported for the first time. The ridge-waveguide DFB laser structure offers the prospect of high modulation speeds due to the absence of parasitic capacitances associated with reverse-biased current-blocking layers. These devices also represent the first report of CW operation of DFB lasers fabricated using the hybrid LPE/MOCVD crystal-growth technique and also of DFB lasers with gratings produced by electron-beam lithography.