What Is the Laser Cavity Threshold Gain & Round-Trip Loss Calculator?
Threshold gain is the optical gain per unit length that the active laser medium must provide so that round-trip optical power remains unity.
How Does the Laser Cavity Threshold Gain & Round-Trip Loss Calculator Work?
Computes mirror coupling transmission loss α_m = (1/2L) · ln[1 / (R₁·R₂)].
Adds internal scattering and crystal defect loss α_s.
Laser Cavity Threshold Gain & Round-Trip Loss Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
g_th = α_s + (1 / 2L) · ln[ 1 / (R₁ · R₂) ]
Round-trip Barkhausen phase and amplitude condition for steady-state laser cavity oscillation.
How to Use the Laser Cavity Threshold Gain & Round-Trip Loss Calculator
- Enter laser cavity length in cm.
- Enter mirror reflectivities R₁ and R₂.
- Specify internal loss coefficient.
Step-by-Step Example Calculation
Solid-State Nd:YAG Rod Resonator
Input Values:
cavityLength:10
mirror1Reflectivity:0.99
mirror2Reflectivity:0.9
internalLoss:0.01
Worked Steps: 10 cm cavity with 90% output coupler and 1% distributed internal loss.
Understanding Your Result
Outputs minimum gain coefficient in cm⁻¹ needed to achieve lasing.
Factors That Affect the Result
- Output coupler reflectivity (lower R₂ increases output power coupling but requires higher pump power to reach threshold).
When Should You Use This Calculator?
- Laser resonator design, diode laser design, and pump threshold power estimation.
Assumptions & Limitations
- Assumes uniform gain distribution along cavity length.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard Siegman laser physics equation.