Refractive indices for extraordinary waves in uniaxial crystals

Divergent beam-based method for measuring the detuning angles of a laser frequency converter

We propose a method to obtain the detuning angles of a frequency converter by tripling the frequency of a divergent Gaussian beam. The frequency tripling process of the divergent beam was first simulated. It is found that the detuning angles of the frequency converter are linearly related to the position of the maximum light intensity point of the third harmonic laser. The corresponding experiment was conducted, and the results agreed well with the theoretical analysis. This method measures the detuning angles of the frequency converter in only one measurement and within 1 min. The detuning angle measurement errors of KDP and KD*P crystals are less than 10 µrad and 36.5-61.9 µrad, respectively.

Precise and versatile formula for birefringent filters

In an investigation of extraordinary- (E-) ray behavior and the index of refraction for E waves in a uniaxial crystal, a precise and versatile formula for birefringent filters, based on the exact construction of the optical path difference, is set up with neither the approximation Δn = n(o) - n(e) ≤ (or n(e)), nor the ambiguity sin(θ)sin(r(ω)) = n(e). The exact construction gives the correct variation of the position and the dimension in each path, yielding the path difference while the filter is tuning. The formula is applicable not only to a filter with its optical axis parallel to the entrance surface (PAPS) but also to a filter with its axis inclined to the surface (PAIS). Also, the formula indicates that a FAIS allows laser wavelengths to be tuned over a wider range than does a FAPS. The origin of the wider range is interpreted to be the greater variation in the index for the FAIS while the filter is tuning. With the help of the formula we design a FAIS for tuning a cw Ti:sapphire laser.