Intracavity gain gratings

Abstract

Intracavity gain gratings are theoretically demonstrated to exhibit diffraction efficiencies that are 100 times larger than unity at pump powers substantially below the lasing threshold. Experiments performed using a Nd:YVO4 microlaser pumped below threshold by two interfering Ti:sapphire laser beams are described. Huge enhancement of the diffraction efficiency (5000X) and a large increase of the angular selectivity (10X) are demonstrated despite the angular reduction of the Fabry-Perot cavity finesse. Much better results are expected using gain gratings with larger areas or thinner cavities such as vertical cavity surface-emitting lasers. Such large fan-out values could be very interesting for applications to optical signal processing.

Bragg diffraction in thin 2D refractive index modulated semiconductor samples

“…The thickness is also an issue as it must not be too large if an integrated device is wanted, although the diffraction regime associated with thin crystals is a Raman-Nath regime involving multiple diffracted beams. Besides the already wellknown simple [2][3][4] and double resonance [5][6][7][8][9] in a Fabry-Perot cavity, a new approach using slow light at the band edge of a one-dimensional photonic crystal (1D-PC) was recently demonstrated to overcome these difficulties, first in photopolymers [10] and then in semiconductor Bragg reflectors [11]. Results are especially attractive in the latter case due to the high index contrast of Bragg reflectors.…”

Efficient Bragg diffraction in thin semiconductor two-dimensional gratings

“…However, their small thicknesses imply a Raman-Nath diffraction regime with several diffraction orders, which limits the maximum power reached in the desired order. Such a drawback was circumvented by placing the holographic material in an asymmetric cavity [6][7][8], and the Bragg operation of the device was obtained, even with a thin recording material [9,10]. Recently, another solution using two-dimensional (2D) photonic crystals was proposed and demonstrated in photopolymers [11].…”