External Ring Resonator Research Articles

A Transmissive Linear Polarization and Circular Polarization Cross Polarization Converter Based on All-Dielectric Metasurface

In this article, we propose a metasurface with C2 symmetry in the terahertz band, which consists of an external ring resonator and an inner double split ring resonator. In order to overcome the problems of ohmic loss and low transmission efficiency caused by the metal structure, we selected all-dielectric materials to design. From 2.17 THz to 2.24 THz, through numerical simulation, the device we proposed can achieve high-efficiency cross-polarization conversion of linearly polarized waves and circularly polarized waves, and their transmission efficiency exceeds 0.8. We first explained it through polarization orthogonal decomposition, and then the physical mechanism is investigated specifically by the distribution of electric field and magnetic field, and the influence of structural parameters on the device is also discussed. In addition, the cell we proposed has a thickness of about λ/10, which is conducive to the design and integration of terahertz devices and systems.

Hybrid III-V Silicon Photonic Integrated Circuits for Optical Communication Applications

This paper summarizes recent advances of integrated hybrid InP/silicon-on-insulator lasers and transmitters based on a wafer bonding technique. First, directly modulated hybrid III-V/Si tunable lasers integrated with an external ring resonator filter are demonstrated, enabling the improvement of the dynamic extinction ratio. An efficient tunable filter is then reported mainly for access applications. Finally, results on integrated distributed feedback laser and electro-absorption modulator at 1.3 μm are presented, showing the capability of operation up to $\text{32}\,\text{Gb}/\text{s}$ . Meanwhile, an integrated tunable laser with an electro-absorption modulator is demonstrated at 1.5 μm, exhibiting excellent bit-error-rate performance at $\text{10}\,\text{Gb}\text{/s}$ .

Strong influence of configuration interactions on the orientation and alignment dichroism in the3pphotoelectron spectra of free laser-polarized Fe atoms

The $3p$ photoelectron spectra of oriented and aligned free Fe atoms are presented. The atomic polarization was achieved by optical pumping. For this purpose single-mode ultraviolet continuous wave laser radiation was produced by second harmonic generation in an external ring resonator. The ground state Fe $3{d}^{6}4{s}^{2}$ $^{5}D_{4}$ was oriented by circularly polarized laser radiation and aligned by linearly polarized laser radiation. Switching from right handed to left handed circularly polarized laser radiation or by changing the polarization angle of the linearly polarized laser radiation by 90\ifmmode^\circ\else\textdegree\fi{} allowed for the measurement of the orientation or the alignment dichroism in the Fe $3p$ photoelectron spectra excited by linearly polarized synchrotron radiation. The spectra are compared to the predictions of the single configuration $LS$-coupling model and the results of single and multiconfiguration calculations. Strong configuration interactions in the final core-hole states manifest themselves in marked deviations from the characteristic patterns. The comparison of the spectra of the free Fe atoms with spectra of thin magnetized Fe films reveals similarities but also marked differences between the dichroism curves of free and bound Fe atoms. The common atomic origin of the dichroism of free and bound Fe atoms is discussed; changes in the intra-atomic electron interactions as well as changes in valence electronic configuration when going from free to bound Fe atoms are addressed.

A laser system for the TESLA photon collider based on an external ring resonator

We present a concept of a laser system for a photon collider at the TESLA linac. It is based on an external optical ring cavity which is pumped by a short-pulse laser. A detailed discussion of the geometry of the external cavity is given.

Second Harmonic Generation and Frequency Stabilization of a Diode Laser Using an External Ring Resonator

The second harmonic light of an 842 nm diode laser was generated from a KNbO3 crystal in an external ring resonator. The power of the second harmonic light was about 0.8 mV at an input fundamental power of 87 mW. The laser frequency was stabilized to the resonance frequency of the ring resonator, and the frequency fluctuation was measured as about 3 MHz.

Generation of high power cw laser light at 257 nm for laser cooling of intense 24 Mg + beams at the ESR

We report on the generation of 750 mW cw laser radiation at a wavelength of 257 nm obtained by frequency doubling the green Ar+ line in a Brewster-cut BBO crystal placed in the spherical focus of an external ring resonator. The system is optimized for laser cooling studies of intense 83.7 MeV 21Mg+ ion beams at the ESR dedicated to the investigation of space charge-dominated beams.

Second-harmonic generation and optical stabilization of a diode laser in an external ring resonator

The second harmonic of the 842-nm output of a GaAlAs diode laser is generated in a KNbO(3) crystal in a resonant, external ring cavity. The diode laser is optically stabilized to the ring cavity through feedback from the counterpropagating fundamental wave, which is weakly excited in the resonator. We have produced 6.7 mW of tunable, narrowband radiation at 421 nm and have used that light to perform saturation spectroscopy on narrow transitions in rubidium.

Generation of tunable ultrashort light pulses by a laser with dynamic distributed feedback in an external ring resonator

Experimental and theoretical studies were made of the time and energy characteristics of a rhodamine 6G dye ring laser with optically induced distributed feedback, pumped synchronously by a train of ultrashort pulses from an actively mode-locked YAG:Nd laser with intracavity second harmonic generation. Narrow-band (~ 0.08 nm) generation of ~ 10 ps ultrashort pulses, tunable in the 568–602 nm range, and with a divergence of ~ 0.4 mrad was achieved. The energy efficiency was ~ 4% for each of the two output beams at a pump energy of 25 μJ. Under optimal conditions the duration of the output pulse was approximately twenty times shorter than that of the pump pulse. The results of the calculations using the proposed model show a good agreement with the experiments.

Efficient Frequency Doubling for Synchronously Mode-Locked Dye Lasers

Generation of high-power, wavelength-tunable UV picosecond laser pulses is commonly believed to require the use of pulse compression and cavity dumping or the use of second harmonic generation in either an intracavity geometry or an external-ring resonator. These approaches use either high peak power or high circulating power to increase the generated UV. However, the addition of a pulse compressor increases the laser linewidth, while the use of a cavity dumper reduces the repetition rate of the laser. Both increase the cost and complexity of the laser system. Intracavity frequency doubling requires modification of the dye laser optics, which slaves the dye laser to UV operation and makes scanning the wavelength difficult. Moreover, the majority of such intracavity designs utilize ring dye lasers, which are more difficult to maintain in proper alignment than are standing-wave dye lasers. External ring resonators require additional optical components and critical matching of the two cavity frequencies. In comparison, we have found that normal, angle-tuned, extra-cavity frequency doubling can produce conversion efficiencies from 1 to 7% by careful adjustment of the dye laser cavity length.

Optical frequency doubling of a single-mode dye laser in an external ring resonator

Optical frequency doubling of a single-mode cw Rhodamin 6G ring dye laser is performed with a thin angle-tuned LiIO3 Brewster cut crystal in a stabilized passive ring resonator. A conversion efficiency of η=5 mW uv/320 mW fundamental input power was achieved at λ=603 nm.

Observation of bistable optical effects in a twin GaAs∕GaAlAs diode external cavity ring laser

Hysteresis, slow quasiregular oscillations and bistability have been observed in the output from a laser system consisting of two antireflection coated GaAs/GaAlAs double heterostructure 20 μm oxide stripe laser diodes symmetrically placed in an external ring resonator.