Electro-optic modulator with ultra-low residual amplitude modulation for frequency modulation and laser stabilization

Area of Science:

• Optics and Photonics
• Spectroscopy
• Laser Physics

Background:

• Residual Amplitude Modulation (RAM) from electro-optic modulators increases system noise in sensitive spectroscopy.
• Reducing RAM is critical for advancing frequency modulation spectroscopy applications.

Purpose of the Study:

• To demonstrate a simple, passive method for reducing RAM in electro-optic modulators.
• To achieve RAM levels comparable to actively controlled modulators using a passive design.

Main Methods:

• Utilizing an electro-optic modulator (EOM) specifically cut at Brewster's angle.
• Characterizing the RAM performance of the Brewster-cut EOM.

Main Results:

• The proposed Brewster-cut EOM exhibits a RAM of a few parts per million.
• This RAM level is comparable to common EOMs requiring active temperature and voltage control.
• The RAM effect from the EOM contributes to frequency instability below 3×10^-17 for a cavity-stabilized laser.

Conclusions:

• A simple passive approach using a Brewster-cut EOM effectively reduces RAM.
• This method offers a low-noise solution for frequency modulation spectroscopy.
• The demonstrated EOM design minimizes laser frequency instability caused by modulation.