Prism Resonator Research Articles

Tiling Photonic Topological Insulator for Laser Applications

A photonic topological insulator is a structure that isolates radiation in the bulk rather than at the edge (surface). Paradoxically, applications of such an insulator focus on its conducting edge states, which are robust against structural defects. We suggest a tiling photonic topological insulator constructed from identical prism resonators connected to each other. The light beam circulates inside the tiling bulk without propagation. However, we experimentally demonstrate a topologically-protected propagating state due to the disconnected faces of the edge resonators. The investigated state is robust against removing or attaching prism resonators. Moreover, the protection principle is phase-free and therefore highly scalable both in wavelength and resonator size. The tiling is suggested for active topological photonic devices and laser arrays.

Wide Temperature Range Laser Based on Conduction‑Cooled End‑Pumped Slab and Crossed‑Porro Prism Resonator

Wide Temperature Range Laser Based on Conduction‑Cooled End‑Pumped Slab and Crossed‑Porro Prism Resonator

Photonic Topological Insulator Based on Frustrated Total Internal Reflection in Array of Coupled Prism Resonators

Total internal reflection occurs at the interface between two media with different refractive indices during propagation of light rays from a medium with a higher refractive index to a medium with a lower refractive index. If the thickness of the second medium is comparable to a specific light wavelength, then total internal reflection is violated partially or completely. Based on the frustrated total internal reflection, herein we discuss a two-dimensional photonic topological insulator in an array consisting of triangular, quadrangular, or hexagonal transparent prism resonators with a narrow gap between them. An array of prism resonators allows topologically stable edge solutions (eigenwaves) similar to those studied in ring resonators. Moreover, total internal reflection occurs at different angles of incidence of light. This makes it possible to obtain a set of fundamentally new edge solutions. The light is presumably concentrated at the surface; however, in the new solutions it penetrates relatively deep into the photonic topological insulator and excites several layers of prisms positioned beyond the surface. Remarkably, the direction of light propagation is precisely biased, and therefore new solutions exhibit lower symmetry than the resonator array symmetry.

Alignment-insensitive end-pumped continuous-wave crossed-Porro prism Ho3+:YAG laser.

A continuous-wave crossed-Porro prism Ho3+:YAG laser is presented and compared with a corresponding mirror resonator. A maximum output power of 30.7 W is reached with a slope efficiency of 67.4% with respect to the absorbed pump power. The laser output beam shows a very good beam quality of better than M2 < 1.2 which clearly surpasses that of the mirror resonator. In terms of alignment sensitivity, the crossed-Porro prism resonator is superior to the mirror resonator due to the retro-reflective nature of the prisms in the axis around the apex.

Comparison of crossed-Porro prism resonator design with conventional mirror resonator design in a Ho3+:YAG laser

Comparison of crossed-Porro prism resonator design with conventional mirror resonator design in a Ho³⁺:YAG laser

A High Q-factor, Easy-to-use, Broadband Ce:LiCAF Laser Cavity Based on Total Internal Reflection

We report a design of a cerium-doped lithium calcium hexafluoro aluminumate (Ce:LiCaAlF\(_{6}\), Ce:LiCAF) laser resonator based on total internal reflection (TIR). This TIR configuration is established by placing the Ce:LiCAF crystal between two calcium fluoride (CaF\(_{2}\)) Pellin-Broca prisms. The laser resonator exhibits a 289-nm emission with 3.5-nm spectral linewidth and 4.4-ns pulse duration. Results show that the present configuration can be a high Q-factor, easy-to-use, broadband prism resonator suitable as a laser oscillator not only in the ultraviolet (UV) region but also down to vacuum ultraviolet (VUV) wavelengths where alignment is restricted to vacuum environments.

XeCl excimer laser with new prism resonator configurations and its performance characteristics.

New resonator cavity configurations, namely, the prism resonator and unstable prism resonator, are demonstrated for the first time in an excimer (XeCl) laser with interesting and novel results. High misalignment tolerance ∼50 mrad is achieved with considerably reduced beam divergence of less than ∼1 mrad without reduction in output power capabilities of the laser. The misalignment tolerance of ∼50 mrad is a dramatic improvement of ∼25 times compared to ∼2 mrad normally observed in standard excimer laser with plane-plane cavity. Increase in depth of focus from 3 mm to 5.5 mm was also achieved in case of prism resonator configuration with an improvement of about 60%. Unstable prism resonator configuration is demonstrated here in this paper with further reduction in beam divergence to about 0.5 mrad using plano-convex lens as output coupler. The misalignment tolerance in case of unstable prism resonator was retained at about 30 mrad which is a high value compared to standard unstable resonators. The output beam spot was completely filled with flat-top profile with prism resonator configurations, which is desired for various material processing applications. Focusing properties and beam divergence in case of prism resonator have been investigated using SEM (scanning electron microscope) images. SEM images of the focused spot size (∼20 μm holes) on metal sheet indicate beam divergence of about 0.05 mrad which is about 1.5 times diffraction limit. Energy contained in this angle is thus sufficient for micro-machining applications. Clean and sharp edges of the micro-holes show high pointing stability with multiple shot exposures. Such characteristics of the excimer laser system will be extremely useful in micro-machining and other field applications.

378 fs pulse generation with Nd3+:SrLaGa3O7 (Nd:SLG) disordered crystal

In this work we present femtosecond pulse generation with a disordered Nd:SLG crystal. By pumping with a Ti:sapphire laser tuned at 808 nm, we obtained pulses as short as 378 fs in a single-dispersive prism resonator employing a semiconductor saturable absorber mirror (SESAM) for mode-locking. Furthermore, sub-picosecond pulses were generated in the 1060–1083 nm spectral range.

Efficient copper vapor laser using metal (Cu, Ag) chlorides in thermal insulation and performance with new prism resonator configurations

A copper vapor laser based on the use of copper chloride and silver chloride mixture embedded inside the laser head thermal insulation is successfully demonstrated. The use of external HCl generator cell containing zirconium chloride normally used for its kinetically enhanced mode of operation is completely eliminated. With this new configuration laser power of ~70 W was achieved from a wide aperture ~47-50 mm bore discharge tube with input power of ~5 kW and overall high efficiency of ~1.4% without external supply of HCl vapors to the laser head. In a typical operational cycle the laser initially operates as low temperature CuCl laser with startup time of few minutes and output power of ~10 W during low tube temperature range of ~300-500 °C. Thereafter, the laser transforms itself into efficient kinetically enhanced copper vapor laser (CVL) at high temperature range of ~1200-1600 °C with maximum laser output power of ~70 W. This dual mode of operation observed in a single CVL system is unique and has not been reported so far in any high temperature copper vapor laser. New resonator configurations, namely, the prism resonator in stable and unstable form are successfully demonstrated for the first time in a copper vapor laser to achieve low divergence beam with dramatic increase in misalignment tolerance to ~25 mrad, which is an improvement of about ~50 times compared to standard CVLs with conventional spherical or plane-plane resonators. With these new resonator configurations the CVL functions almost as an "alignment free laser" system with significantly reduced beam divergence of ~0.2 mrad and high optical extraction efficiency of ~70%-80%.

Size-Independent Prism Resonator Partially Filled With DNG Metamaterial

A cavity resonator in the shape of a prism with a square base and walls that are either perfect electric or perfect magnetic conductors is considered. The resonator consists of two identical prisms with triangular bases, filled respectively with a double-positive material and a double-negative metamaterial, the two materials having opposite refractive indexes and the same intrinsic impedance. It is shown that electromagnetic fields whose electric or magnetic field is parallel to the height of the prism may exist for any dimensions of the cavity.

Kaleidoscope modes in large aperture Porro prism resonators

We apply a new method of modeling Porro prism resonators, using the concept of rotating loss screens, to study stable and unstable Porro prism resonator. We show that the previously observed petal--like modal output is in fact only the lowest order mode, and reveal that a variety of kaleidoscope beam modes will be produced by these resonators when the intra--cavity apertures are sufficiently large to allow higher order modes to oscillate. We also show that only stable resonators will produce these modes.

Jones matrix formulation of a Porro prism laser resonator with waveplates: theoretical and experimental analysis

This article presents the results of a detailed theoretical and experimental analysis carried out on a folded Z-shaped polarization coupled, electro–optically Q-switched laser resonator with Porro prisms and waveplates. The advantages of adding waveplates in a Porro prism resonator have been explored for creating high loss condition prior to Q-switching and obtaining variable reflectivity with fixed orientation of Porro prism. Generalized expressions have been derived in terms of azimuth angles and phase shifts introduced by the polarizing elements. These expressions corroborate with known reported results under appropriate substitutions. A specific case of a crossed Porro prism diode-pumped Nd:YAG laser has been theoretically and experimentally investigated. In the feedback arm, a 0.57λ waveplate oriented at 135° completely compensates the phase shift of a fused silica Porro prism and provides better tolerances than a BK-7 prism/0.60λ waveplate combination to stop prelasing. The fused silica prism/0.57λ combination with waveplate at 112° acts like a 100% mirror and was utilized for optimization of free running performance. The effective reflectivity was determined for various orientations of the quarter waveplate in the gain arm to numerically estimate the Q-switched laser pulse parameters through rate equation analysis. Experimental results match well with the theoretical analysis.

Petal-like modes in Porro prism resonators

A new approach to modeling the spatial intensity profile from Porro prism resonators is proposed based on rotating loss screens to mimic the apex losses of the prisms. A numerical model based on this approach is presented which correctly predicts the output transverse field distribution found experimentally from such resonators.

Verification of first circulation conditions of turnstile waveguide circulators using a finite-element solver

One means of adjusting the first circulation condition of any waveguide circulator is to have recourse to a finite-element (FE) solver. The purpose of this paper is to do so for each of the three possible geometries of the turnstile waveguide circulator. A complete statement of the first circulation condition also requires one of the susceptance slope parameter of the junction. This quantity is separately evaluated. The resonators under consideration are the side and apex coupled half-wave-long prism structures open circuited at each flat face and the conventional cylindrical geometry. The classic E-plane turnstile circulator using a prism resonator is also dealt with. The agreement between the existing literature and the FE adjustment is excellent.

Formation of the fundamental transverse mode in the resonator of a laser with electrooptical reflecting gate during autoinjection of initiating radiation

The optical diagram of a single-pulse laser with autoinjection of initiating free-running laser radiation, which ensures the development of the fundamental transverse mode in a prism resonator with an electrooptical reflecting gate, is studied experimentally.

Polarisation inhomogeneities of a ring resonator and nonreciprocity of counterpropagating waves

The nonreciprocity of the characteristics of counterpropagating waves in a ring resonator formed by totally reflecting prisms is analysed. The polarisation-inhomogeneous properties of a prism resonator and their effect on the nonreciprocity of the frequencies of counterpropagating waves are studied.

Mode chart and susceptance slope parameter of an E-plane circulator using coupled prism resonators

A three-port E-plane circulator may be constructed by placing either a pair of quarter-wave long cylindrical or prism resonators open-circuited at one end and short-circuited at the other in the H-plane of its junction. In the paper, the mode chart of the prism resonator arrangement is developed, and measurements on its susceptance slope parameter are taken. Since there is more than one solution that will meet the midband frequency of this sort of circulator, the susceptance slope parameter is not single valued. Knowledge of these two quantities satisfies the first classic circulation condition of the device.

Folded prism resonators for slab lasers with high beam quality

Different types of resonators built with prisms and spherical mirrors were investigated with respect to their practicability for slab lasers. The beam parameter product could be improved from θ· w=100 mrad mm for a normal slab system to 20 mrad mm, with a total efficiency of 3.3% resulting in an output power of 250 W. A further decrease down to 5 mrad mm was achieved with an off-axis prism resonator, but at a reduced efficiency.

Off-axis prism resonator for improved beam quality of slab lasers

An off-axis prism resonator that was especially designed for slab lasers is investigated. It consists of an output coupling mirror and two 90-deg prisms, one of which is placed off axis. This arrangement permits a fill factor of one and reduces the mode order of the extracted beam compared with that of a conventional stable mirror resonator. Thus a high extraction efficiency and high beam quality are achieved.

Lateral displacement of the mode axis in a misaligned Porro prism resonator

The lateral shift of the mode axis in a misaligned Porro prism resonator is analyzed. A method to find the tilted mode axis in a misaligned Porro prism resonator is introduced. Expressions for the displacement of the mode axis are deduced. They predict that the lateral displacement of the mode axis is proportional to the horizontal misalignment angle beta and highly dependent of the prism azimuth angle theta. Experimental results obtained agree well with theory.