All Solid-State Raman Lasers

Updated July 2004

Yellow, orange and red laser sources based on stimulated Raman scattering

Co-workers

• Helen Pask
• Jim Piper

Group Activities:

• Thermal effects in Raman lasers
• High-average power yellow lasers for medical applications
• Coupled-cavity, external cavity and intra-cavity architectures
• New IR, vis and UV wavelengths
• Multi-wavelength operation

Raman lasers employing crystalline Raman media such as potassium gadolinium tungstate and barium nitrate form the basis of an all-solid-state technology for generating moderate average power in the yellow - orange spectral region. Practical sources in this spectral range are of increasing interest for applications in medicine, remote sensing and visual display applications, but are not easily obtained using conventional solid-state lasers.

Example: External KGW Raman resonators pumped at 532nm

By changing the output coupler and Raman crystal orientation, more than 8 wavelengths in the yellow-to-red spectral region were generated including 555 nm, 559 nm, 579 nm, 589 nm, 606 nm, 622 nm, 636 nm and 658 nm, ie., the first 4 Stokes orders on the two orthogonal high-gain Raman shifts of KGd(WO4)2. We have also demonstrated spectrally pure output (typically >90% pure) for selected Stokes order with output power up to 400 mW. High slope efficiency (up to 68%) and high beam quality (M2~1.5) of Stokes output are obtained even at the highest pump power.

Simultaneous output on 4 Stokes orders (plus fundamental pump) with total output power 0.5W

Top view of the external cavity KGW Raman laser

Key achievements:

• For an intracavity Raman laser with intracavity frequency-doubling, we obtained 1.7W at 579 nm at 7% diode-to-yellow conversion efficiency.
• Using an external-cavity Raman resonator pumped by a 1 W 532 nm laser, we obtained output at more than 8 wavelengths in the range 555 nm to 658 nm with output powers as high as 0.4 W at slope efficiencies up to 68%.