Calculator Inputs
Frequency mode expects THz inputs. Wavelength mode expects nm inputs. The calculator uses energy conservation and a simplified phase-matching efficiency estimate.
Plotly Graph
The graph sweeps the signal frequency across the selected span and plots idler frequency and idler wavelength trends.
Formula Used
1) Energy conservation in difference frequency generation
fi = |fp - fs|
2) Wavelength from frequency
λ = c / f
3) Coherence length
Lc = π / |Δk|
4) Phase matching factor
PM = sinc²(ΔkL / 2)
5) Relative conversion index used here
Index ∝ (deff² · Pp · L²) / (npnsniAeff) × sinc²(ΔkL / 2)
This efficiency-related output is a practical scaled indicator, not a full rigorous coupled-wave solution. It helps compare setups quickly under consistent assumptions.
How to Use This Calculator
- Choose whether you want to enter frequency values or wavelength values.
- Enter the pump and signal inputs using the selected mode.
- Fill crystal length, nonlinear coefficient, pump power, beam radius, and refractive indices.
- Enter phase mismatch in rad/mm for coherence and phase-matching estimates.
- Set graph sweep span and the number of sweep points.
- Press Calculate DFG to show the results above the form.
- Review the result table, graph, and export options.
Example Data Table
These sample rows help demonstrate how the calculator behaves with different pump, signal, and phase mismatch values.
| # | Pump (THz) | Signal (THz) | Idler (THz) | Idler Wavelength (nm) | Crystal Length (mm) | Δk (rad/mm) | Coherence Length (mm) |
|---|---|---|---|---|---|---|---|
| 1 | 300.000 | 280.000 | 20.000 | 14,989.623 | 20.00 | 0.100 | 31.416 |
| 2 | 290.000 | 250.000 | 40.000 | 7,494.811 | 15.00 | 0.050 | 62.832 |
| 3 | 350.000 | 315.000 | 35.000 | 8,565.499 | 25.00 | 0.120 | 26.180 |
| 4 | 220.000 | 180.000 | 40.000 | 7,494.811 | 12.00 | 0.080 | 39.270 |
FAQs
1) What is difference frequency generation?
Difference frequency generation is a nonlinear optical process where two input waves interact inside a suitable crystal and create an idler wave at the frequency difference.
2) What does the idler frequency represent?
The idler frequency is the generated output frequency. In this calculator, it is found from the absolute difference between pump and signal frequencies.
3) Why is phase mismatch important?
Phase mismatch controls how efficiently optical waves stay in step while traveling through the crystal. Better matching usually supports stronger frequency conversion.
4) What is coherence length?
Coherence length is the distance over which the interacting waves stay nearly phase aligned. Larger coherence length generally indicates more favorable interaction conditions.
5) Is the conversion index an exact efficiency?
No. It is a scaled comparison metric based on simplified assumptions. It is useful for screening trends, not for replacing a full device simulation.
6) Can I use wavelengths instead of frequencies?
Yes. Switch the input mode to wavelength, enter values in nanometers, and the calculator converts them internally before evaluating the idler output.
7) Why does the calculator need refractive indices?
The refractive indices help shape the relative conversion estimate. They affect how strongly the fields interact in the simplified scaling expression.
8) When should I use this calculator?
Use it for quick DFG feasibility checks, educational demonstrations, parameter comparison, and early-stage nonlinear optics planning before deeper modeling.