Crystal Nonlinear Optics with SNLO Examples: A Practical Guide to Simulation and Design

Introduction

Nonlinear optics (NLO) is the backbone of modern photonics, enabling technologies such as frequency doubling, optical parametric oscillation (OPO), and terahertz generation. At the heart of these processes are nonlinear optical crystals—materials like BBO, KTP, and LiNbO₃—whose phase-matching properties dictate device performance. However, designing a nonlinear optical experiment or device requires more than just selecting a crystal; it demands precise calculation of phase-matching angles, walk-off, effective nonlinear coefficients, and conversion efficiencies. This is where SNLO (Software for Nonlinear Optics) becomes indispensable.

SNLO Exercises and Examples (PDF): A direct list of examples keyed to specific SNLO functions. It covers topics like second-harmonic generation (SHG), OPO/OPA phase matching, and linear pulse propagation .

SNLO output: Angular tuning curve, threshold vs. pump spot size.

  1. SNLO → "OPO Angle Tuning".
  2. Crystal: KTP (Type II, x-cut or z-cut, typically x-cut for 532 nm pumping).
  3. Pump wavelength: 0.532 µm.
  4. Signal range: 0.7–0.9 µm (set manually).
  5. Compute: The program outputs signal and idler wavelengths vs. internal angle.
  6. For a given angle (e.g., 54° internal), signal = 790 nm, idler = 1630 nm.
  7. Use "OPO Threshold" module: Input mirror reflectivities (say 99% for signal, 80% for idler) → threshold pump intensity ~30 MW/cm².