Zero-Offset Frequency Locking of Lasers At Low Optical Powers With an Optical Phase Locked Loop

• Frequency locking of lasers is fundamental to a vast number of applications within the field of optics. Usually, when locking a laser to an optical reference wave, it is imperative that locking can be maintained in spite of low reference powers. Previous solutions to frequency locking involve injection locking and/or optical phase locked loops. While previous works have shown locking to weak waves, we extend the lowest demonstrated optical power locked to by approximately 20 dB, realizing locking down to -90 dBm, using a novel digital dither optical phase-locked loop. Measurements of the locked laser phase error verify the performance. The loop design circumvents the presence of a dither on the locked laser light, hence avoiding dither penalties, and low-power locking is realized via coherent detection gain without any optical amplifiers. Low phase noise standard deviations of less than 20°at -80 dBm optical power and Allan deviation of $3\cdot 10^{-16}$ at 1 s averaging time indicate great potential for a variety of applications within optical sensing, communications, and metrology.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Teknisk mekanik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Applied Mechanics (hsv//eng)

Nyckelord

Optical receivers

Optical phase-locked loop

sensing

Optical fiber sensors

Optical amplifiers

Optical pumping

Optical noise

Communications

phase noise

Low power

metrology

Optical fibers

Adaptive optics

laser frequency locking

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