Technical Note: Second-Harmonic Generation With IMRA's FCPA μJewel

By IMRA America, Inc.

This note describes a simple set-up for second-harmonic generation (also known as "frequency-doubling") of an FCPA μJewel to obtain green, pulsed light using off-the-shelf components.

Among the various nonlinear crystals available (BBO, KTP, BiBO, KNbO₃, PPLN, etc.), we recommend the use of LBO for the following reasons:

• Non-Critical Phase Matching (NCPM) condition
  • No walk-off
  • Large acceptance angle → ease of alignment
    Since the energy per pulse from the FCPA μJewel changes for different repetition rates, different focusing conditions are required for optimal conversion.
• Small Group Velocity Mismatch (GVM) allows longer crystal to be used → greater SHG output
• High damage threshold Intensity = 45 GW/cm², τ = 100 ps @ λ = 532 nm