The compactization of lasers is an ongoing challenge in increasing their effectiveness and integrability of other systems, from nanosatellites to medical devices. The need to decrease their dimensions, especially, for diode-pumped solid-state microchip laser systems causes significant problems with beam quality. Such lasers feature an additional problem of Brightness to output power scaling power. We report an approach where we used a thin film dielectric Fano-like resonance structure as a replacement to a conventional output coupler to overcome this challenge. The structure is engineered to function as a flat spatial filter element for selecting the fundamental transverse mode of the cavity. We achieved an increase of 2x over a conventional setup in CW operation. The data matches well with the numerical analysis performed for a single longitudinal mode model. We predict that this discovery could lead to advanced power scaling in submillimeter cavities, while maintaining the beam quality.
This work presents the investigation of 2D periodic structures made by conformal deposition of dielectric thin films on the modulated surface, where the deposited layers repeat the primary surface. Depending on the architecture, spatial filtering and polarization control may be performed in transmission or reflection with the incidence of radiation perpendicular to the surface.
In the presentation, the overview of different technologies to form conformal coatings on periodically modulated surfaces will be presented. As the proposed 2D photonic structure can be considered a promising component for intracavity spatial filtering, the integration into a microchip laser will be presented. A significant reduction of M2 and brightness increase of two times was recorded for the microchip laser when the fabricated spatial filter was used as one of the resonator mirrors.
The transverse modes in microchip lasers (MCL) appear different from the classical mode theory, as the resonator consists of a set of plane mirrors (similar to semiconductor edge-emitting lasers and VCSELs). Then the parabolic potential is absent, and the electromagnetic radiation is confined in the transverse space of the resonator by other mechanisms, essentially by gain guiding. Thermal lensing also can play some role in confining the radiation. Laser engineers use several intuitive assumptions about the number of supported modes in the resonator, relating with the Fresnel number of the resonator. However, despite some attempts to calculate the modes in such resonators and investigate combined gain with index guiding, no clear and straightforward methods were provided to calculate the beam radiation profiles. We aim to fill this gap by providing analytical and numerical treatment of MCL modes in two dimensions. We analyze the transverse modes in microchip laser formed due to both gain guiding and thermal lensing. Analytical and numerical results are compared with the results of experimental measurements. Using the cylindrical pumping profile approach, we provide a simple 2D theory of the gain-guided and thermal-lens induced modes in such plane-mirror resonators. We estimate the mode beam quality factor dependency on pumping strength. The model is versatile and applicable to wider range of optical resonators consisting of plane mirrors with longitudinal pumping. Finally, we compare the experimental measurements of beam quality factor with our theoretical model.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.