Distributed feedback broad area lasers with multiple epitaxially stacked active regions and tunnel junctions.

Distributed feedback (DFB) broad area (BA) lasers with multiple epitaxially stacked active regions and tunnel junctions designed for emission around 900 nm are investigated. DFB BA lasers with a cavity length of 1 mm and different stripe widths are compared in terms of their electro-optical performance and beam quality. The laser with a 200 µm stripe width achieved a high optical pulse power of 100 W in 10 ns long pulses at an injection current of 63 A, resulting in a brightness of 81 MW/cm2sr. The optical spectrum of both lasers is centered at around 886 nm, exhibiting a narrow spectral bandwidth of 0.2 nm (64 pm/K).

Comparison of individual and common wavelength-operation for 785 nm Y-branch DBR ridge waveguide diode lasers with adjustable spectral distance.

An experimental comparison between individual and common wavelength-operation of a Y-branch distributed Bragg reflector (DBR) ridge waveguide (RW) laser at 785 nm with an electrically adjustable spectral distance is presented. The dual-wavelength Y-branch laser combines two laser cavities via a Y-section to a common output section. DBR gratings with different grating periods are associated with the two cavities, which set the emission wavelengths of the two branches. Implemented resistive heater elements allow separate wavelength tuning of the two branches, which can be operated individually for alternating emission wavelengths in applications such as differential absorption spectroscopy or shifted excitation Raman difference spectroscopy. Common wavelength operation simultaneously generates two emission lines suitable for the generation of THz radiation using difference frequency mixing. Hereby, the devices could potentially be used as single-chip light sources for a combination of Raman and THz applications. For the wavelength-operation comparison presented, the devices were operated up to optical output powers of about 105 and 185 mW in individual and common wavelength-operation mode, respectively. In individual operation mode, the devices show spectral single-mode emission over the whole operation range. In common operation mode, the spectral emission is predominantly single mode up to an optical output power of 65 mW. In both operation modes, mode hops typical for DBR lasers occur. At an optical output power of 50 mW, tuning of the spectral distance between the two wavelengths using the implemented resistor heaters is demonstrated. In both modes of wavelength operation, a flexible frequency difference between 0 and 0.8 THz (0 and 1.6 nm) with predominantly single-mode spectral emission is obtained.

783 nm wavelength stabilized DBR tapered diode lasers with a 7 W output power.

Wavelength stabilized distributed Bragg reflector (DBR) tapered diode lasers at 783 nm will be presented. The devices are based on GaAsP single quantum wells embedded in a large optical cavity leading to a vertical far field angle of about 29° (full width at half maximum). The 3-inch (7.62 cm) wafers are grown using metalorganic vapor phase epitaxy. In a full wafer process, 4 mm long DBR tapered lasers are manufactured. The devices consist of a 500 µm long 10th order surface DBR grating that acts as rear side mirror. After that, a 1 mm long ridge waveguide section is realized for lateral confinement, which is connected to a 2.5 mm long flared section having a full taper angle of 6°. At an injection current of 8 A, a maximum output power of about 7 W is measured. At output powers up to 6 W, the measured emission width limited by the resolution of the spectrometer is smaller than 19 pm. Measured at 1/e2 level at this output power, the lateral beam waist width is 11.5 µm, the lateral far field angle 12.5°, and the lateral beam parameter M2 2.5. The respective parameters measured using the second moments are 31 µm, 15.2°, and 8.3. 70% of the emitted power is originated from the central lobe.

Continuous-wave operation of DFB laser diodes based on GaN using 10$

Single longitudinal mode continuous-wave operation of distributed-feedback (DFB) laser diodes based on GaN is demonstrated using laterally coupled 10th-order surface Bragg gratings. The gratings consist of V-shaped grooves alongside a 1.5 µm wide p-contact stripe fabricated by using electron-beam lithography and plasma etching. By varying the period of the Bragg grating, the lasing wavelength could be adjusted between 404.8 and 408.5 nm. The feasibility of this device concept was confirmed by mode-hop-free operation up to an optical output power of 90 mW, a low temperature sensitivity of the lasing wavelength, and a Gaussian lateral far-field distribution.

Extended 9.7 nm tuning range in a MOPA system with a tunable dual grating Y-branch laser.

In this Letter, we present a tunable Y-branch hybrid master oscillator power amplifier (MOPA) with 5.5 W output power, emitting between 973.7 and 983.4 nm. The MO is a monolithic Y-branch distributed Bragg reflector (DBR) diode laser, which is collimated and coupled into a tapered amplifier using cylindrical microlenses in a compact 25 mm×25 mm conduction cooled laser package. The wavelength spacing between the two laser branches is 2.2 nm. Each branch can be electrically tuned by up to 7.5 nm of quasi-continuous wavelength tuning, which in combination covers up to 9.7 nm of spectral range. Over this range, an output power variation of 0.5% and 0.2% is observed for the left and right arms, respectively, while maintaining a spectral width of less than 17 pm. In addition, the MOPA system can be operated as a dual-wavelength system by operating both branches simultaneously. The presented device is suitable for nonlinear frequency conversion applications.

Dual-wavelength diode laser with electrically adjustable wavelength distance at 785 nm.

A spectrally adjustable monolithic dual-wavelength diode laser at 785 nm as an excitation light source for shifted excitation Raman difference spectroscopy (SERDS) is presented. The spectral distance between the two excitation wavelengths can be electrically adjusted between 0 and 2.0 nm using implemented heater elements above the distributed Bragg reflector (DBR) gratings. Output powers up to 180 mW at a temperature of 25°C were measured. The spectral width is smaller than 13 pm, limited by the spectrum analyzer. The device is well-suited for Raman spectroscopy, and the flexible spectral distance allows a target-specific adjustment of the excitation light source for shifted excitation Raman difference spectroscopy (SERDS).

Dual-wavelength Y-branch distributed Bragg reflector diode laser at 785 nanometers for shifted excitation Raman difference spectroscopy.

A dual-wavelength Y-branch distributed Bragg reflector (DBR) diode laser at 785 nm is presented as an excitation light source for shifted excitation Raman difference spectroscopy (SERDS). The monolithic device was realized with deeply etched surface DBR gratings using one-step epitaxy. An optical output power of 140 mW was obtained in continuous-wave (CW) operation for each laser cavity, with emission wavelengths of the device at 784.50 and 785.12 nm. A spectral width of the laser emission of 30 pm (0.5 cm(-1)), including 95% of optical power, was measured. The mean spectral distance of both excitation lines is 0.63 nm (10.2 cm(-1)) over the whole operating range. Raman experiments using polystyrene as the test sample and ambient light as the interference source were carried out and demonstrate the suitability of the dual-wavelength diode laser for SERDS.

Tapered lasers emitting at 650 nm with 1 W output power with nearly diffraction-limited beam quality.

High-brightness tapered lasers emitting around 650 nm were developed. Devices 2 mm long with a200-microm-long straight section, 1800-microm-long tapered section, and 4 degrees taper angle reached 1 W output power in CW operation with a nearly diffraction-limited beam quality.