Phase-Locking and Coherent Power Combining of Broadband Linearly Chirped Optical Waves
Abstract
We propose, analyze and demonstrate the optoelectronic phase-locking of optical waves whose frequencies are chirped continuously and rapidly with time. The optical waves are derived from a common optoelectronic swept-frequency laser based on a semiconductor laser in a negative feedback loop, with a precisely linear frequency chirp of 400 GHz in 2 ms. In contrast to monochromatic waves, a differential delay between two linearly chirped optical waves results in a mutual frequency difference and an acoustooptic frequency shifter is therefore used to phase-lock the two waves. We demonstrate and characterize homodyne and heterodyne optical phase-locked loops with rapidly chirped waves, and show the ability to precisely control the phase of the chirped optical waveform using a digital electronic oscillator. A loop bandwidth of ~60 kHz, and a residual phase error variance of < 0.01 rad squared between the chirped waves is obtained. Further, we demonstrate the simultaneous phase-locking of two optical paths to a common master waveform, and the ability to electronically control the resultant two-element optical phased array. The results of this work enable coherent power combining of high-power fiber amplifiers- where a rapidly chirping seed laser reduces stimulated Brillouin scattering- and electronic beam steering of chirped optical waves.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 05, 2012
- Accession Number
- ADA579953
Entities
People
- Amnon Yariv
- Arseny Vasilyev
- George Rakuljic
- Jeffrey O. White
- Naresh Satyan
Organizations
- California Institute of Technology