Zoom

NKT Photonics offers PM photonic crystal fibers that incorporate a non-circular core in combination with the large refractive index step between air and glass; this creates strong form birefringence. The result can be a shorter beat length that reduces the bend-induced coupling between polarization states compared with conventional PM fibers, and a much reduced thermal sensitivity of birefringence. The temperature coefficient of birefringence of these fibers is up to 30 times less than that of other leading stress-birefringent fibers.

Zoom

NKT Photonics' polarization-maintaining (PM) highly nonlinear photonic crystal fibers guide light in a small solid silica core, surrounded by a microstructure cladding formed by a periodic arrangement of air holes in the silica. The optical properties of the core closely resemble those of a slightly elliptical rod of glass suspended in air; this results in a strong confinement of the light, a large nonlinear coefficient, and a substantial splitting of the effective indices of the polarization modes. The zero-dispersion wavelength has been chosen for use with Ti:Sapphire laser sources, but the dispersion is also anomalous at the fundamental Neodymium wavelength (1060 nm).

The term supercontinuum generation includes many nonlinear effects that lead to a substantial spectral broadening. These nonlinear effects include Raman scattering, self-phase modulation and solitons. Supercontinuum spectra are typically produced by inputting short (femtosecond range) high power pulses into a nonlinear medium. Since the dispersion in a photonic crystal fiber can be tailored to facilitate the generation of supercontinuum spectra in a specific region, nonlinear photonic crystal fibers are an attractive media.

Supercontinuum (SC) sources are a new type of light source that combine the high radiant power and high degree of spatial coherence of a laser with a spectral bandwidth usually associated with an incandescent source. Supercontinuum sources can often drastically improve the signal-to-noise ratio, reduce the measurement time, or widen the spectral range in applications that require a broadband source, including high-resolution spectroscopy, the characterization of optical components, or optical coherence tomography (OCT). Despite the complex nature of the non-linear optical processes that convert the narrowband output of a laser into a supercontinuum, the practical realization can be surprisingly straight forward. All that is required is a high peak power pulsed laser, and a non-linear element with the right dispersion characteristics. The high power density, long length at comparatively low loss and the ability to achieve zero dispersion at wavelength shorter than 1250 nm - something that is not achievable with conventional fibers - makes small-core PCF ideally suited as the nonlinear element in a SC source. NKT Photonics offers small-core fibers suitable for use with femtosecond Ti:sapphire lasers (NLxx-xxx), as well as a fiber specifically designed to generate SC radiation from the output of a compact, low-cost Nd3+-YAG microchip laser (SC-5.0-1040). Please see detailed application note linked below for more information.

When selecting a fiber for supercontinuum generation, the relationship between a fiber’s zero dispersion wavelength and the pump is the most important consideration. The table below provides a general guideline for cases when pumping the photonic crystal fiber with femtosecond laser sources. The attached pdf file offers more details regarding supercontinuum generation using the NL series of Photonic Crystal Fiber.

Supercontinuum - General Application Note - Thorlabs.pdf