Three-mirror resonator with aspheric feedback mirror for laser spatial mode selection and mode shaping

Fabrication of large-sag aspheric micro-optics with nanometer accuracy using electron-beam lithography on curved substrates

“…18 Since the extendedcavity VCSEL has three collinearly aligned mirrors ͑two distributed Bragg reflectors and one aspheric mirror͒, the aspheric mirror design and the laser modal analysis have to be conducted in the context of the coupled-cavity effect. 4 Each of the aspheric mirrors has a surface profile closely matching the wavefront of a diffracted flattop mode, whose beam waist is at a given distance from the mirror.…”

“…We have recently demonstrated laser mode control and mode shaping in an extended-cavity laser resonator by using an aspheric third mirror collinearly aligned with a two-mirror Fabry-Perot resonator. 4,18 In an extended-cavity laser resonator, the combination of the center mirror and the aspheric third mirror serves as a phase-conjugate etalon to provide the phase-conjugate reflection for the desired cavity mode. The fabrication of the aspheric optics is very critical and significantly affects the laser performance.…”

“…One recent application of aspheric optics is inside laser cavities. Aspheric laser-cavity optics have been demonstrated to perform many advanced functions such as mode shaping, 2,3 singlemode selection, 4 and thermal-aberration correction. 5 Many aspheric optics for laser applications have been fabricated as diffractive elements whose phase is a 2-wrapped version of the desired profile ͑or a -wrapped version in the case of diffractive mirrors, because the light travels through an element twice on reflection͒.…”

The applications of aspheric feedback mirror in extended-cavity laser resonators

“…However, analytical modal solutions are difficult to obtain for a complicated cavity structure, especially when the cavity mirror curvatures are allowed to deviate away from simple spherical shapes. We have developed novel simulation methods for analyzing resonator modes and designing aspheric mirrors for extended-cavity lasers 15 .…”

“…The aspheric mirror design for an extended-cavity resonator is more complicated due to the coupled-cavity effect: The eigenmodes of the extended-cavity resonator are different from the eigenmodes of the individual uncoupled subcavities, and the aspheric mirror in an optimized resonator design does not have to be a fixed phase-conjugate mirror for the desired fundamental mode. We have developed the concept of a phase-conjugate etalon to describe the operation of this coupled cavity 15 . Under the guidance of this concept, aspheric mirrors can be designed for mode control and mode shaping in an extended-cavity resonator.…”