Phase-locked fiber interferometer with high frequency, low voltage fiber-stretcher and application to optical field reconstruction

摘要

Light carries a great deal of information in the form of amplitude, phase, and polarization, any or most powerfully all, of which may be exploited for the characterization of materials or development of novel technologies. However, extracting the full set of information carried by light becomes increasingly difficult as sample feature sizes shrink and the footprint and cost of detection schemes must decrease as well. Here, a fiber-based interferometric scheme is deployed to extract this information from optical systems which may be assessed three dimensionally down to the nanoscale and/or temporally up to the bandwidth of electronic data acquisition available. The setup utilizes a homemade fiber stretcher to achieve phase-locking of the reference arm and is compatible with heterodyning. More interestingly, a simplified and less expensive approach is demonstrated which employs the fiber stretcher for arbitrarily frequency up-converted (with respect to driving voltage frequency) phase modulation in addition to locking. This improves the detection system's size, weight, power, and cost requirements, eliminating the need for an acousto-optic modulator and reducing the drive power required by orders of magnitude. High performance is maintained as evidenced by imaging amplitude and phase (and inherently polarization state) in micro and nano optical systems such as lensed fibers and focusing waveguide grating couplers previously imaged only for intensity distribution.