1. Ferdinand-Braun-Institut
  2. Research
  3. Research News
  4. Compact diode laser modules wi ...

Compact diode laser modules with single-mode fiber output in the multi-watt power range

FBH research: 04.03.2015

Butterfly module with single-mode fiber output

Fig. 1: Photograph of the butterfly module with single-mode fiber output

Optical power and coupling efficiency vs. taper current

Fig. 2: Optical power and coupling efficiency vs. taper current

Efficient and compact laser light sources emitting spectrally narrow-band near-infrared (NIR) radiation in continuous-wave (CW) operation at high-output powers in a spatially fundamental mode are desired for numerous applications. These include pumping of solid-state lasers and frequency conversion. Within the InnoProfile-Transfer joint research project "FaBriDi", the Ferdinand-Braun-Institut (FBH) develops fiber-coupled demonstrators for unrestricted industrial use. Project partners are C2GO inprocess solutions, FCC FibreCableConnect, and eagleyard Photonics.

Recently, a butterfly module with a footprint of less than 10 cm2 has been successfully demonstrated. It comprises a highly brilliant distributed Bragg reflector (DBR) tapered diode laser emitting around 1064 nm, a micro-optical assembly designed to maintain brightness and mounted with sub-micrometer precision, and temperature-stabilizing components. The module is also equipped with a single-mode fiber (SMF) output with standard FC/APC connector (Fig. 1). With this assembly, an efficient, multi-watt laser light source is available that is characterized by a narrow-band spectrum and a stigmatic, nearly Gaussian laser beam independent of the optical power level.

The power of the assembled butterfly module ex SMF increases nearly linearly with the injection current into the taper section, as can be observed in Fig. 2. A maximum power ex SMF of 2.5 W is reached at a coupling efficiency of 57%. However, the single-frequency operation of the DBR tapered diode laser is disturbed at some taper current values, at which multiple peaks in the spectral distribution can be observed. This spectral instability could be attributed to back reflections from the fiber facets. Nonetheless, the optical spectrum of the butterfly module remains within 0.3 nm in the investigated taper current range. The laser beam ex SMF is axially symmetric with nearly Gaussian intensity profiles in the beam waist and the far field. The beam propagation parameter M2 is determined to 1.0 (1/e2) and 1.4 (2nd order moments) at a power level ex SMF of 2.1 W through a caustic measurement.

This ongoing work is funded by the German Federal Ministry of Education and Research under contract No. 03IPT613A. The module design is currently being optimized in order to provide higher optical power. In future, modules emitting at further wavelengths, such as 976 nm and 920 nm, as well as modules with a low-mode-number fiber output will be demonstrated.

Publications

D. Jedrzejczyk, P. Asbahr, M. Pulka, B. Eppich and K. Paschke, "Coupling of DBR tapered diode laser radiation into a single-mode-fiber at high powers", Proc. SPIE, vol. 8965, Photonics West, San Francisco, USA, Feb. 1-6, 89651A (2014).

D. Jedrzejczyk, P. Asbahr, M. Pulka, B. Eppich, and K. Paschke, "High-Power Single-Mode Fiber Coupling of a Laterally Tapered Single-Frequency Diode Laser", IEEE Photonics Technol. Lett., vol. 26, no. 8, pp. 845-847 (2014).

Outlook: D. Jedrzejczyk et al., "Coupling of a high-power tapered diode laser beam into a single-mode-fiber within a compact module", to be published in SPIE Proc. 9348 (2015).

FBH research: 04.03.2015