Triangular Ring Laser Research Articles

Characterizing relative intensity noise in InGaAsP-InP triangular ring lasers

This paper discusses relative intensity noise (RIN) characterization of triangular ring lasers, fabricated through a self-aligned dry etching process in InGaAsP-InP. Unusual low frequency noise enhancement was observed in each of the output beams, that is strongly dependent on the mirror backscattering strength. We explain the physical origin of the unusual RIN results as a partition noise effect between the two output beams of the ring laser, which can be best interpreted as superposition of two incoherent spatially bidirectional modes, generated by incoherent spontaneous emission photons traveling in clockwise and counterclockwise directions. This effect is unique to the ring laser geometry, and reported here for the first time. General noise predictions of our analysis are consistent with experimental measurements. This partition noise enhancement is expected to be present in the entire class of bidirectional semiconductor ring lasers, affecting the noise performance of not only the triangular ring laser, but also circular and square geometries, and possibly microdisk type lasers, in integrated photonic circuit applications.

Triangular laser resonators with astigmatic compensation

The magnitudes and locations of the beam waists in both the sagittal and the tangential planes have been found by means of the ABCD matrix method for a triangular resonator. Equilateral and isosceles resonators are discussed, and curves are given from which resonators with astigmatism-free beams can be designed. A frequency-doubled triangular Nd ring laser has been constructed after this design, and it is demonstrated that this laser emits a single longitudinal mode with a circular TEM(00) Gaussian beam.

Spatial beam switching and bistability in a diode ring laser

We report bistable switching of the output direction in certain triangular diode ring lasers. These lasers operate unidirectionally at large drive currents, with up to 98% of the output power emerging from either the clockwise or the counterclockwise direction. The preferred direction can switch back and forth, with a large hysteresis loop, as the drive current is varied. Up to 20 mW of optical power changes direction at each switch. We propose an explanation based on the theory of two-mode competition via gain saturation.

Design of a triangular active ring laser 13 m on a side

The design and testing of a proof-of-principle triangular active ring laser interferometer ~13 m on a side is discussed. Issues such as lock in, multimode interference, mode hopping, and neon isotope mixtures are examined as they relate to large He-Ne ring lasers. Responses of the ring laser to Earth's rotation and perturbations that change its tilt or area are presented. Some potential applications are suggested for large interferometers.

Long-wavelength triangular ring laser

Single-lateral mode, long-wavelength, waveguide diode-ring lasers have been fabricated in InP-InGaAsP with facets etched using CAIBE. The devices lase at around 1.26 /spl mu/m under pulsed testing. The lowest threshold current is around 64 mA, The best side-mode-suppression ratio (SMSR) is found to be 25.4 dB. Triangular ring lasers demonstrated significantly higher SMSR than Fabry-Perots fabricated on the same chip. Ring laser far-field and output power dependence on structural angle are also reported.

Unidirectional operation of waveguide diode ring lasers

A method of providing asymmetric feedback in the triangular ring laser structure was devised through the simple alterations of the waveguide shape. Two kinds of alterations were designed and implemented, one being the “optical diode,” the other being the tapered waveguide. Unidirectional operation was achieved for the ring lasers, with a single-beam slope efficiency of 0.23 W/A, which was the highest single-beam slope efficiency reported for semiconductor ring lasers.

Scattering matrix analysis of a triangular ring laser

A method of analysis for ring waveguide lasers is presented. This method is based on the use of the scattering matrix formulation to represent the waveguide junctions. An extension of previous work is made so that any number of junctions may be serially connected. The method is then applied to a three-junction triangular ring laser and various operating characteristics are calculated, in particular the longitudinal mode spacing and the power ratio of the counterpropagating waves of the laser. It is found that this ratio is much more sensitive to a difference in forward coupling than to backward coupling, but that a difference in either will enhance unidirectional operation of the device. Comparison to experimental data is made where possible.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Reflection and transmission of a dielectric waveguide mirror

A numerical analysis of a generalized dielectric waveguide mirror of arbitrary structure angle is presented. A plane wave expansion technique is used to calculate output angle, power transmission, inter-waveguide and intra-waveguide coupling, far-field emission profile and losses of the waveguide mirror. In order to evaluate the effect of divergence, two methods are used and the result indicate that the effect is minimal. Furthermore, the introduction of a tilt in the mirror surface is examined and reveals a reduction in the inter-waveguide coupling as the tilt is increased. However, this coupling remains symmetric in tilt despite the asymmetry of the geometry due to the tilt. Results of the output angle and the FWHM (full-width half-maximum) of the emission profile are compared to experimental values obtained for a semiconductor triangular ring laser.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

リングレーザを用いた角度の測定

An experimental study for high precision digital angle measurement by using a He-Ne ring laser is described. The triangular ring laser, which is composed of an invar framework with a cavity length of 180 cm and two plasma tubes filled with 14 : 1 : 1 mixture of He : Ne20 : Ne22 discharged with current-stabilized power supplies is used. Angles (30°) of twelve sides constituting a polygon are measured applying the principle that the integral of beat signal of the ring laser is directly proportional to the angle of rotation of the ring laser. The dispersion of the measured values is found to be 10"-45" for 30°. It has become clear that it is important to supress fluctuation of cavity length much less than the present level and to operate on stable single mode for better accuracy.

Fresnel Drag in a Ring Laser: Measurement of the Dispersive Term

The Fresnel drag has been measured in a triangular ring laser at a wavelength of 0.6328 \ensuremath{\mu}. The drag coefficient in fused silica is $\ensuremath{\alpha}=0.541\ifmmode\pm\else\textpm\fi{}0.003$, while the theory, including the dispersion term, gives ${\ensuremath{\alpha}}_{\mathrm{theor}}=1\ensuremath{-}(\frac{1}{{n}^{2}})\ensuremath{-}\ensuremath{\beta}(\frac{\ensuremath{\lambda}}{n})$ $\frac{\mathrm{dn}}{d\ensuremath{\lambda}}=0.5423$ with $\ensuremath{\beta}=1$. The coefficient $\ensuremath{\beta}$ is thus determined as $\ensuremath{\beta}=0.87\ifmmode\pm\else\textpm\fi{}0.22$, which includes the classical value $\ensuremath{\beta}=1$. Thus the magnitude of the drag in a ring laser is within the errors equal to that given in an inertial frame of reference (linear drag).

Polarization Properties of a Triangular Ring Laser Having a Discharge Tube with Brewster Angle Windows

The polarization properties of ring resonators for the case of a single discharge tube with Brewster angle windows in the optical circuit are investigated. The azimuths of polarization of the traveling waves and the related reflection losses due to the Brewster angle windows are calculated as a function of the orientation angle of the Brewster angle windows for different anisotropic reflectances of the reflecting mirrors of the resonators. The experiments are made on a triangular ring laser which is operated at the 6328 A He-Ne line. The measured polarization and intensity of the output light agree very well with the theoretical predictions.