FBH research: 04.03.2019

Micro-integrated laser sources with watt level output power in the yellow-green spectral range

Butterfly housing with yellow-green laser sources
Custom butterfly housing with micro-integrated yellow-green micro-integrated laser sources
SHG output power in relation to fundamental input power into PPLN crystal
SHG output power shown in relation to the fundamental input power into the PPLN crystal

The FBH has succeeded in developing a very compact laser module emitting in the yellow-green spectral range at 561 nm and 574 nm with power levels in the watt range. The diode-based laser system, measuring only 76x54x15 mm³, uses a novel butterfly housing and is aimed at biomedical and spectroscopic applications. These laser modules are used, for example, in ophthalmology and high-resolution confocal microscopy. In cw mode, they achieve output powers of more than 2 W at 561 nm and 1.5 W at 576 nm in free space configuration.

Since no direct emitting lasers with high spectral brightness are available in the wavelength range from 560 nm to 580 nm, the FBH uses its powerful, highly coherent NIR laser sources to generate visible light via second harmonic generation in single pass configuration. The modules presented here feature a full semiconductor master oscillator power amplifier (MOPA) in combination with nonlinear crystals made of periodically poled lithium-niobate. A micro-optical isolator is integrated to shield the laser structure against back reflections, thereby retaining the spectral properties of the emission. Furthermore, the MOPA approach allows for direct modulation without affecting the emission wavelength.

This module class offers the possibility of a polarization-maintaining single-mode fiber output. The emission is characterized by a polarization extinction ratio of > 20 dB and a spectral width around 1 MHz. In the near future, the new laser modules will enable a significantly higher degree of miniaturization of laser systems for medical applications.

Publications

A. Sahm, N. Werner, J. Hofmann, R. Bege, and K. Paschke, "Compact Miniaturized Laser Module Emitting More Than 1.6 W of Yellow Light at 576 nm", IEEE Photonics Technol. Lett., vol. 30, no. 21, pp. 1878-1881 (2018).

A. Sahm, N. Werner, J. Hofmann, D. Jedrzejczyk, D. Feise, and K. Paschke, "Miniaturized watt-level laser modules emitting in the yellow-green spectral range for biophotonic applications", Proc. SPIE, 10902-11 (2019).