A Review of Progress about Birefringent Filter Design and Application in Ti:sapphire Laser

Abstract

All-solid-state tunable lasers have been widely used in many fields including multi-photon microscopy, time-resolved photoluminescence, atomic physics, and so on owing to their broadband output spectrum range, good beam quality, and low noise. To cover the broad fluorescent line of the laser crystal as much as possible, a birefringent filter (BRF) is always the most popular candidate for acting as a tuning element. In this review, the tuning characteristics of BRF and the design rule as well as its progress in practical application are summarized. Especially, it is worth noting that laser crystal itself begins to act as the BRF for wavelength tuning except for its gain characteristic, which has paved a new way for developing a kind of novel tunable laser. We believe that this review will not only provide a valuable reference for the design of BRF but also lay the foundation for developing a new application of BRF.

Methods of Radiation Wavelength Tuning in Short-Pulsed Fibre Lasers

“…The key parameters of the reviewed lasers are given in Table 1. The mechanisms used for creation of wavelength-dependent losses include polarisation effects (birefringent spectral filters [86] introducing minimal losses for radiation that does not change polarisation when passing through the filter; polarisation controller(s) [45,69,73,81] or intra-cavity waveplates [83], whose function is essentially similar to that of a birefringent filter; intensity-dependent variation of birefringence in the cavity [84,85]; Sagnac loop mirror [87] with spectrally controlled reflection), interference effects (various interferometers: Fabry-Pérot [88], Mach-Zehnder [89], and so on), dispersion effects (prisms [90], diffraction gratings [64,68,76,82], acousto-optical filters [49,77]). The majority of the wavelength tuning mechanisms used in pulsed fibre lasers are known; they were earlier applied to other types of lasers.…”