1. Linewidth: "Frequency Accuracy" of Lasers
Linewidth is a key indicator to measure the spectral purity of the laser, which refers to the full width at half maximum (FWHM) of the laser output spectrum. The linewidth of narrow linewidth lasers is usually at the kHz (kilohertz) level or even lower.
- The narrower the linewidth, the more stable the frequency of the laser and the stronger the coherence;
- The wider the linewidth, the greater the frequency fluctuation and the poorer the coherence.
The external cavity narrow linewidth laser source (3/5kHz) mentioned in the picture achieves stable output of a single longitudinal mode through the advanced active fiber DFB short straight cavity structure, ensuring an extremely narrow linewidth.
2. Stability: The "Frequency Consistency" of Lasers
Stability refers to the degree of fluctuation of the output frequency of the laser during long-term operation. Lasers with high stability can maintain frequency consistency under external interference such as temperature changes and mechanical vibrations.
- Small frequency drift: For example, the frequency drift of the laser mentioned in the picture can be controlled within 1 MHz/°C;
- Low phase noise: Ensure the purity of the laser signal;
- Precise temperature control: A high-precision temperature control system is used to ensure the stable operation of the laser.
Stability is crucial for applications such as fiber optic sensing and spectral analysis. Any frequency fluctuation may cause measurement errors or signal distortion.
3. Signal-to-noise ratio: The "signal purity" of the laser
Signal-to-noise ratio (SNR) is an important indicator for measuring the quality of the laser output signal, which refers to the ratio of signal power to noise power.
- High signal-to-noise ratio: means that the laser signal is pure and the noise interference is small;
- Low signal-to-noise ratio: the signal is mixed with more noise, affecting the system performance.
Narrow linewidth lasers achieve high signal-to-noise ratio through single longitudinal mode output and low noise design, providing reliable guarantee for precision measurement and high-speed data transmission.
4. The relationship between core indicators
Linewidth, stability and signal-to-noise ratio are interrelated and jointly determine the performance of narrow linewidth lasers:
- Narrow linewidth helps to improve frequency stability and signal-to-noise ratio;
- High stability ensures the long-term consistency of linewidth;
- High signal-to-noise ratio reflects the combined effect of linewidth and stability.
Therefore, when selecting, these three indicators need to be considered comprehensively to meet the needs of specific applications.
5. Application value: wide range of uses from communication to scientific research
Narrow linewidth lasers are widely used in:
- Optical communication: improve signal transmission rate and distance;
- Fiber optic sensing: improve measurement accuracy and sensitivity;
- Spectral analysis: achieve high-resolution spectral measurement;
- Scientific research: such as atomic cooling, gravitational wave detection, etc.
6. Conclusion: Performance is king above indicators
The linewidth, stability and signal-to-noise ratio of narrow linewidth lasers are the three core indicators to measure their performance. Only lasers that perform well in these three aspects can play a real role in high-end applications.