Dual-Wavelength Diode Laser for Raman Spectroscopy

Novel diode lasers for portable and miniaturized measurement systems based on Raman spectroscopy are developed. Two separate sections and implemented gratings on a single chip are used for alternating emission on two different wavelengths.

These innovative diode lasers are used for the spectroscopic SERDS (Shifted Excitation Raman Difference Spectroscopy) method allowing Raman spectroscopic measurements under, e.g., highly fluorescent conditions. With SERDS, the limit of detection can be improved by more than one order of magnitude compared to conventional Raman spectroscopy. With the rice grain-sized monolithic light source, a compact Raman probe will be realized for the first time for SERDS which is only as small as a laser pointer. The project establishes the basis for an unique miniaturized Raman spectroscopic system which will be used for in situ measurements in application fields like, e.g., security, biology, medicine, food control, and pharmaceutical industry. Furthermore, this concept enables applications including absorption spectroscopy and the generation of THz radiation.

  • Dual-wavelength Y-branch diode laser
    [+] Dual-wavelength Y-branch diode laser
  • Diode laser on C-mount
    [+] Diode laser on C-mount

Functional principle

The semiconductor chip has a footprint of 0.5 mm x 3 mm and includes two laser cavities. Two DBR laser mirrors are realized with a spectral distance of 10 cm-1. An integrated Y-branch coupler provides a common output aperture. Separate electrical contacts allow individual control for both emission wavelengths.

Applications

  • Excitation light source for Raman spectroscopy and Shifted Excitation Raman Difference Spectroscopy – SERDS

Typical Wavelengths

  • 671 nm
  • 785 nm

Technology and Mounting

  • Semiconductor structures with MOVPE
  • High order surface DBR grating

Typical Data

  • 671 nm
    100 mW optical power for Y-DBR-RW diode laser
  • 785 nm
    200 mW optical power for DBR-RW diode laser
    750 mW optical power for Y-DBR MOPA diode-laser system
  • Spectral Width ≤ 10 pm

These diode lasers are developed in the project DiLaRa funded by the Federal Ministry of Education and Research (BMBF) within the program "Validierung des Innovationspotentials wissenschaftlicher Forschung – VIP" and is supported by the project executing agency VDI/VDE Innovation + Technik GmbH (funding period: 01.12.2011 - 30.11.2014).