Source: NASA Technology Transfer Program

The Nonplanar Ring Oscillator Laser: A Compact and Stable Design

Introduction

A nonplanar ring oscillator (NPRO) laser is a type of laser oscillator known for its stable, compact, and rugged design. It utilizes a special monolithic structure that enhances its performance and reliability.

Design and Operation

The resonator of an NPRO laser consists of a single laser crystal, typically made of materials like Nd:YAG or Yb:YAG. The laser light circulates within the crystal, with one surface coated with a partially reflective dielectric mirror that serves as the output coupler. This design allows for unidirectional oscillation, crucial for stable single-frequency operation.

Importance of Nonplanar Resonator

The nonplanar nature of the ring resonator in an NPRO introduces a slight rotation of the polarization direction in each round-trip, enabling unidirectional operation. This feature helps avoid standing-wave patterns and spatial hole burning, leading to stable laser performance.

Spectral Properties and Laser Noise

NPRO lasers have a short round-trip length, resulting in a relatively large free spectral range for continuous frequency tuning. Various methods, such as crystal temperature adjustment or pump power modulation, can be used for tuning. The stable mechanical setup and low optical losses contribute to very low laser noise levels, with typical linewidths in the kilohertz range.

Applications

NPRO lasers are commonly used as master lasers in high-power single-frequency MOPA (master oscillator power amplifier) systems. Their compact size, stability, and low noise make them ideal for applications requiring precise and reliable laser sources.

Conclusion

In summary, nonplanar ring oscillator lasers offer a unique design that combines stability, compactness, and low noise characteristics. Their monolithic structure and unidirectional operation make them valuable tools in various laser applications where high performance is essential.

Source: Oxxius – Simply Light
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