Microsystem-based External Cavity Diode Laser

External cavity diode lasers with narrow band emission in the red spectral range are developed and used as excitation light sources for Raman spectroscopy. These compact devices are realized using microoptical components and enable portable Raman-measurement systems for the application in biology, medicine, and pharmacy. Currently, these diode lasers are used for in situ characterization of meat quality.
Moreover, this concept has been extended, and diode lasers are realized for Shifted Excitation Raman Difference Spectroscopy (SERDS).

  • Microsystem light source at 671 nm for SERDS
    [+] Microsystem light source at 671 nm for Shifted Excitation Raman Difference Spectroscopy - SERDS
  • 671 nm ECL microsystem light source for Raman spectroscopy
    [+] 671 nm ECL microsystem light source for Raman spectroscopy

Functional principle

A broad area or tapered laser diode is mounted on a micro-optical bench. The rear facet of this device is anti-reflection coated. On the back side microptics direct the beam to a reflecting Bragg grating (RBG). This RBG stabilizes the emission wavelength and its spectral width of typically 100 pm.

Applications

  • Excitation light source for Raman spectroscopy and Shifted Excitation Raman Difference Spectroscopy (SERDS)
  • Pump source for the non-linear frequency conversion

Wavelengths

  • 671 nm
  • 785 nm

Technology and Mounting

  • Semiconductor structures with MOVPE
  • Broad area and tapered diode lasers with anti reflection coated rear facets
  • Active alignments on a micro-optical bench

Typical data

  • Broad area devices with a stripe width of 100 µm reaching an output power of 1.5 W at 671 nm
  • Tapered device with 5 W peak power at 671 nm
  • Spectral line width smaller than 100 pm (95% of the power)
  • Reliable operation over 14500 hours
  • Compact module

These diode lasers were developed in the BMBF project FreshScan supported by the project executing agency VDI/VDE Innovation + Technik GmbH (funding period: 01.07.2006 - 31.12.2009).