Kalman filtering-enhanced short-delay self-heterodyne interferometry for linewidth measurement

Area of Science:

• Physics
• Optical Engineering
• Signal Processing

Background:

• Accurate laser linewidth measurement is crucial for various applications.
• Conventional methods for linewidth measurement can be complex and require specific equipment.
• Short-delay self-heterodyne interferometry (SDSHI) offers a promising approach but can be affected by noise.

Purpose of the Study:

• To develop an enhanced linewidth measurement technique for short-delay self-heterodyne interferometry (SDSHI).
• To improve the accuracy and convenience of laser linewidth estimation.
• To leverage extended Kalman filtering (EKF) for adaptive signal processing in interferometric measurements.

Main Methods:

• Modified SDSHI trace analysis to approximate a biased cosine wave.
• Application of extended Kalman filtering (EKF) for adaptive tracking of the cosine wave signal.
• Utilizing uniform envelope contrast for direct linewidth estimation without correction factors.

Main Results:

• Demonstrated a kHz laser linewidth measurement using the EKF-enhanced SDSHI approach.
• Achieved effective suppression of measurement noise through adaptive filtering.
• Enabled linewidth estimation at each tracked data point, allowing for statistical parameter extraction (mean, standard deviation).

Conclusions:

• The EKF-enhanced SDSHI method provides a convenient and accurate approach for laser linewidth measurement.
• The technique requires no additional equipment beyond conventional SDSHI and EKF implementation.
• This method holds significant potential for widespread application in ultra-narrow laser linewidth metrology.