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.

Subject headings

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

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

Keyword

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

Publication and Content Type

art (subject category)

ref (subject category)