G. Blume

High-Power DBR-Tapered Laser at 980 nm for Single-Path Second Harmonic Generation

We present experimental results about edge-emitting distributed-Bragg-reflector-tapered diode lasers emitting at 980 nm. The investigated lasers show an output power of up to 12 W with a conversion efficiency of about 45%. The lasers also exhibit a small vertical divergence <15deg full-width at half maximum (FWHM), a nearly diffraction-limited beam quality, and a narrow spectral linewidth with FWHM smaller than 12 pm. These properties allow efficient single-pass second harmonic generation with power levels of more than 1 W at 488 nm.

20W continuous wave reliable operation of 980nm broad-area single emitter diode lasers with an aperture of 96μm

High power broad area diode lasers provide the optical energy for all high performance solid state and fiber laser systems. The maximum achievable power density from such systems is limited at source by the performance of the diode lasers. A crucial metric is the reliable continuous wave optical output power from a single broad area laser diode, typically for stripe widths in the 90-100 μm range, which is especially important for users relying on fibered multi-mode pumps. We present the results of a study investigating the reliable power limits of such 980nm sources. We find that 96μm stripe single emitters lasers at 20°C operate under continuous wave power of 20W per emitter for over 4000 hours (to date) without failure, with 60μm stripe devices operating reliably at 10W per stripe. Maximum power testing under 10Hz, 200μs QCW drive conditions shows that 96μm stripes reach 30W and 60μm stripes 21W per emitter, significantly above the reliable operation point. Results are also presented on step-stress-studies, where the current is step-wise increased until failure is observed, in order to clarify the remaining reliability limits. Finally, we detail the barriers to increased peak power and discuss how these can be overcome.

96 mW longitudinal single mode red-emitting distributed Bragg reflector ridge waveguide laser with tenth order surface gratings

Red-emitting ridge waveguide lasers with integrated tenth order surface distributed Bragg reflector gratings were developed. The grating was implemented by the use of a BCl3-Ar-plasma, while the shape of the grating trench was controlled by additional He-backside cooling of the wafer. The devices exhibit longitudinal single mode operation up to 96 mW at 635.3 nm with a side mode suppression ratio of 18 dB and a good beam quality of M2<3. The spectrum is free of mode hops for a span of more than 55 pm.

Compact second-harmonic generation laser module with 1 W optical output power at 490 nm

We demonstrate continues-wave 1 W at 490 nm on a 2.5 cm(3) micro-optical bench using single-path second-harmonic generation with a periodically poled MgO:LiNbO(3) bulk crystal. The pump laser is a distributed Bragg reflector tapered diode laser having a single-frequency spectrum and a pump power of 9.5 W. Based on that 1 W blue light could be achieved resulting in an optical conversion efficiency of 11%. Furthermore, the module has an output power stability of better than 2% and the blue laser beam shows an nearly diffraction limited beam quality of M(2)(sigma) = 1.2 in vertical and M(2)(sigma) = 2 in lateral direction.

High-power distributed Bragg reflector ridge-waveguide diode laser with very small spectral linewidth

We manufactured and investigated distributed Bragg reflector ridge-waveguide diode lasers having sixth-order surface gratings and an emission wavelength around 974 nm. The single-mode output power of the lasers with a total length of 4 mm exceeded 1 W. A very small spectral linewidth of 1.4 MHz (3 dB) consisting of a Lorentzian part of 146 kHz and a Gaussian part of 1308 MHz was measured using a self-delayed heterodyne measurement technique.

High-spectral-radiance, red-emitting tapered diode lasers with monolithically integrated distributed Bragg reflector surface gratings

A red-emitting tapered diode laser with a monolithically integrated distributed Bragg reflector grating is presented. The device is able to emit up to 1 W of spectrally stabilized optical output power at 5°C. Depending on the period of the tenth order surface grating the emission wavelengths of these devices from the same gain material are 635 nm, 637 nm, and 639 nm. The emission is as narrow as 9 pm (FWHM) at 637.6 nm. The lateral beam quality is M(2)(1/e(2)) = 1.2. Therefore, these devices simplify techniques such as wavelength multiplexing and fiber coupling dedicating them as light sources for µ-Raman spectroscopy, absolute distance interferometry, and holographic imaging.

Watt-level second-harmonic generation at 589 nm with a PPMgO:LN ridge waveguide crystal pumped by a DBR tapered diode laser.

A DBR tapered diode laser in continuous wave operation was used to generate second-harmonic radiation at 589 nm in a PPMgO:LN ridge waveguide crystal. An optical output power of 0.86 W at an optical-to-optical and an electrical-to-optical efficiency of 42% and 11%, respectively, was achieved. The visible radiation was characterized by a spectral bandwidth ΔνFWHM of 230 MHz and a beam propagation parameter M1/e22 better than 1.1. The integration of such a system into a housing of a small footprint will enable a portable and highly efficient module featuring a visible output power in the watt-level range.

Monolithic 626 nm single-mode AlGaInP DBR diode laser

Single-mode lasers below 630 nm are still realized using complex laser systems. We present distributed Bragg reflector (DBR) ridge waveguide lasers (RWL) based on AlGaInP. When packaged into sealed TO-3 housings and cooled internally to about 0°C the DBR-RWL emit more than 50 mW at a wavelength of 626.0 nm into a nearly diffraction-limited single longitudinal mode with a spectral width below 1 MHz. These new monolithic diode lasers have the potential to drastically miniaturize existing set-ups e.g. for quantum information processing.

High luminance tapered diode lasers for flying-spot display applications

Flying-spot display applications require high luminance (> 100 TCd/m2) red-emitting lasers. High luminance is defined as a high optical output power and a nearly diffraction limited beam quality at a wavelength with a good visibility of the human eye. Diode lasers, with all their beneficial properties such as direct modulation capability, small size and good electro-optical efficiency, are so far unable to achieve such high luminance, due to catastrophic optical mirror damage (COMD) caused by high facet loads. (See manuscript for full abstract.)

High-power (1.1W) green (532nm) laser source based on single-pass second harmonic generation on a compact micro-optical bench

We demonstrate a compact high-power green (532nm) laser module based on single-pass second harmonic generation. The pump source is a distributed Bragg reflector tapered diode laser. The frequency conversion is achieved with a 2.5 cm long periodically poled MgO:LiNbO3 bulk crystal. The entire module is integrated on a compact micro-optical bench with a footprint of 2.5 cm3. Up to 1.1 W output green light power is achieved at a pump power of 7.6 W with an optical conversion efficiency of about 15% and a corresponding module wall-plug efficiency of more than 4%. The green laser beam has a relatively good beam quality (measured at output power level of ~0.9 W) with M²σ=1.8 in the vertical direction and M²=4.9 in the lateral direction, respectively. The long-term output power stability is ±10% (tested at output power level of ~0.6 W).