Super-tunable, broadband up-conversion of a high-power CW laser in an engineered nonlinear crystal.

A specially-designed chirped periodically poled lithium niobate nonlinear crystal was fabricated with a phase-matching bandwidth as large as 50 nm for sum frequency generation to operate at room and higher temperatures. This device also benefits from insensitivity to laser frequency drift and fine alignment. The loosely-focused beam position of a high-power CW laser at around 1550 nm is optimized within the grating for maximum up-conversion efficiency, to realize a super-tunable source in the range of 770-778 nm by tuning a narrowband control signal over 30 nm in the communication band.

Design, fabrication and characterization of a specially apodized chirped grating for reciprocal second harmonic generation.

A specially-designed apodized chirped PPLN based on particular positioning of poled regions within the periods has been realized theoretically and experimentally to demonstrate the reciprocal response in the SHG spectra over a 30-nm bandwidth, for up-chirp and down-chirp directions. The simulation results are compared with another apodized chirped PPLN for which the placement of poled regions is deviated from optimum positions. The average power difference is less than 0.

Tailoring and tuning of the broadband spectrum of a step-chirped grating based frequency doubler using tightly-focused Gaussian beams.

We demonstrate theoretically and experimentally, that the non-uniform spectra of second harmonic generation (SHG) from an unapodized step-chirped periodically poled nonlinear optical grating can be apodized utilizing tightly-focused Gaussian beams to suppress the ripple in its wideband response. In our example, by increasing focusing, a ripple-free response is progressively achieved over a 6-dB bandwidth of >5 nm, with a beam waist of 20 µm. With this tight focusing arrangement, a continuous tuning of 11-nm is also demonstrated by simply changing the focal point by 5.

Tunable single-to-dual channel wavelength conversion in an ultra-wideband SC-PPLN.

We experimentally demonstrate tunable dual channel broadcasting of a signal over the C-band for wavelength division multiplexed (WDM) optical networks. This is based on cascaded χ(2) nonlinear mixing processes in a specially engineered, 20-mm-long step-chirped periodically poled lithium niobate with a broad 28-nm second harmonic (SH) bandwidth in the 1.55-μm spectral range.

Agile multicasting based on cascaded χ(2) nonlinearities in a step-chirped periodically poled lithium niobate.

We experimentally demonstrate the possibility of agile multicasting for wavelength division multiplexing (WDM) networks, of a single-channel to two and seven channels over the C band, also extendable to S and L bands. This is based on cascaded χ(2) nonlinear mixing processes, namely, second-harmonic generation (SHG)-sum-frequency generation (SFG) and difference-frequency generation (DFG) in a 20-mm-long step-chirped periodically poled lithium niobate crystal, specially designed and fabricated for a 28-nm-wide SH-SF bandwidth centered at around 1.55 μm.