Integrated-optic double-ring resonators with a wide free spectralrange of 100 GHz

Integrated-optic double-ring resonators with a wide free spectral range (FSR) of 100 GHz are fabricated using GeO₂-doped silica waveguides with a high relative refractive index difference (Δ) of 1.5%. The resonators are composed of two ring resonators comprising small ring waveguides with radii of 1.75 and 2.0 mm. The double-ring resonator module exhibited a wide FSR of 98.0 GHz, a finesse of higher than 138, a low crosstalk of less than -11.7 dB, and a low insertion loss of 6.1 dB. The measured FSR of 98.0 GHz is wider than any previously reported ring resonator composed of optical waveguides     

Polymer microring coupled-resonator optical waveguides

We present measurements of the transmission and dispersion properties of coupled-resonator optical waveguides (CROWs) consisting of weakly coupled polymer microring resonators. The fabrication and the measurement methods of the CROWs are discussed as well. The experimental results agree well with the theoretical loss, waveguide dispersion, group delay, group velocity, and group-velocity dispersion (GVD). The intrinsic quality factors of the microrings were about 1.5/spl times/10/sup 4/ to 1.8/spl times/10/sup 4/, and group delays greater than 100 ps were measured with a GVD between -70 and 100 ps/(nm/spl middot/resonator). With clear and simple spectral responses and without a need for the tuning of the resonators, the polymer microring CROWs demonstrate the practicability of using a large number of microresonators to control the propagation of optical waves.     

A GaInAsP-InP double-ring resonator coupled laser

A monolithic single-mode GaInAsP-InP double microring resonator coupled laser is demonstrated for the first time. The laser comprises two passive ring resonators, semiconductor optical amplifiers in the bus waveguides, and 3-dB codirectional couplers. The laser has an output power of 0.5 mW with a sidemode supression ratio of >35 dB. The tunability is demonstrated using integrated platinum resistors on top of the waveguides in the rings.     

Critical coupling and its control in optical waveguide-ringresonator systems

The coupling of optical waveguides to ring resonators holds the promise of a new generation of switches (modulators) which employ orders of magnitude smaller switching (modulation) voltages (or control intensities). This requires a means for voltage (or intensity) control of the coupling between the waveguide and the resonator. Schemes for achieving such control are discussed     

A wide-FSR waveguide double-ring resonator for optical FDMtransmission systems

A wide free-spectral-range (FSR) waveguide double-ring resonator (DRR) is investigated for use in optical frequency-division multiplexing (OFDM) transmission systems. It consists of two ring resonators with different radii and three directional couplers. The FSR is determined by the least common multiple of the FSRs of the two ring resonators. In order to determine the parameters of the DRR, transmission equations of the DRR, which have different radii, are derived by using the scattering matrix. The dependence of the transmittance characteristics of the DRR on the amplitude coupling coefficients of directional couplers and on the propagation loss of the ring waveguides is studied. The design guidelines for OFDM transmission systems are described     

Thermal analysis of bond layer influence on performance of an all-active vertically coupled, microring resonating laser

The vertical coupling of active InP based ring resonators and passive feeding waveguides necessitates the use of a waferbonding technology in the fabrication process. The required bond material (BCB) has a low thermal conductivity and will strongly influence the operating temperature and thus the performance of the ring resonator through its insulating effect. A comprehensive thermal analysis of a proposed vertically coupled ring resonator of 50 μm outer radius is undertaken during the design phase to determine the thermal impact of: the design of the wafer bond, the design of the passivation layer and the optical power levels. Thermal abatement strategies for semiconductor lasers are presented.     

Ring resonators composed of GeO2-doped silica waveguides

Ring resonators composed of GeO₂-doped silica waveguides fabricated on silicon substrates by a flame hydrolysis deposition method are described. GeO₂-doped silica waveguides are developed to provide a lower propagation loss than that of TiO₂ -doped silica waveguides. Since the finesse and transmission at resonance is determined mainly by total loss in the ring, the loss characteristics of the fundamental components are investigated in detail. Experimental and theoretical investigations show that a finesse of the ring resonator for GeO₂-doped silica waveguides is about 2.7 times higher than that for TiO₂-doped silica waveguides with the same transmission at resonance     

Frequency stabilization of laser diode using a frequency-locked ring resonator to acetylene gas absorption lines

The frequency stabilization of a 1.5 mu m distributed-feedback (DFB) laser diode using a planar lightwave circuit (PLC) ring resonator whose resonant frequency is locked to /sup 12/C/sub 2/H/sub 2/ and /sup 13/C/sub 2/H/sub 2/ gas absorption lines is described. The resonant frequency of PLC ring resonator was stabilized within a 5 MHz peak-to-peak fluctuation. With this ring resonator the outer frequency fluctuation of the DFB laser diode was stabilized within 10 MHz at every resonant frequency at 5 GHz intervals. The stability demonstrated is as good as the method using molecular absorption lines as a reference. The stabilized frequency can be selected at any point on the optical resonant peaks of the optical resonator.<>     

二氧化硅光波导环形谐振腔

利用宽角光束传输法(WA-BPM)对二氧化硅平面波导环形谐振腔进行了优化设计,详细分析了不同环形腔长度下,谐振腔清晰度与环形腔耦合器耦合系数的关系,并进一步分析了由光探测器散弹噪声所限制的谐振型光学陀螺极限灵敏度和环形腔光路参量之间的关系。在此基础上,在硅衬底上利用火焰水解化学掺GeO2的二氧化硅波导上制作成带输入/输出耦合器的环形谐振腔芯片。并通过实验测试了所研制的光波导环形谐振腔,其清晰度高达60,理论分析表明采用上述环形谐振腔研制的陀螺,其极限灵敏度可达1°/h。     

A canonical formulation for analyzing multielement unstable resonators

A simple but general formulation for the unified analysis of many different varieties of unstable optical resonators is obtained by expressing the round-trip Huygens' integral for the resonator in terms of the round-trip paraxial ray matrix. Complicated multielement resonators, ring resonators, and unstable resonators with variable-reflectivity output mirrors are thereby all reduced to a single equivalent collimated-beam diffraction problem. Essential assumptions in the analysis are that all elements in the resonator obey paraxial ray theory and that there is only one significant output coupler or limiting aperture per round trip inside the resonator. The only parameters needed to describe an arbitrary unstable resonator in this formulation are the round-trip magnificationMand either the equivalent Fresnel number Neqor else an equivalent collimated Fresnel numberN_{c} = [2M^{2}/(M^{2} - 1)] N_{eq}, plus for variable-reflectivity mirrors a specification of the mirror reflectivity profile.     

Analysis of four-port optical fiber ring and loop resonators usinga 3×3 fiber coupler and degenerate two-wave mixing

A theoretical analysis of four-port optical fiber ring and loop resonators using a 3×3 fiber directional coupler and degenerate two-wave mixing is presented. Expressions for the circulating (resonant) and output fields and intensities, as well as resonance conditions for two slightly different configurations of the loop resonator and for the ring resonator are obtained. It is found that the use of the degenerate two-wave mixing greatly improves the characteristics of these resonators. For example, the crosstalk of the ring or loop resonators when used as a wavelength division demultiplexer can be significantly deduced     

Transmission, group delay, and dispersion in single-ring optical resonators and add/drop filters-a tutorial overview

This tutorial describes the transmission, group delay time and quadratic dispersion properties of the four basic building blocs of optical filters built using ring resonators. These building blocs are single-ring resonators in either two-port (all-pass) or four-port (add/drop filter) configuration. The effect of waveguide and coupler loss is included throughout. Explicit expressions to compute the complex amplitude of the circulating wave in the ring, the Q factor, the finesse and the insertion loss are also given. Attention is drawn to the similarities between the ring resonator the Fabry-Pe/spl acute/rot resonator and the Gires-Tournois interferometer. Material properties and fabrication technology are not reviewed.     

Laser Stabilization on a Fiber Ring Resonator and Application to RF Filtering

The potential of optical fiber ring resonators for radio frequency (RF) or microwave signals filtering on optical carriers is demonstrated on a short length high Q resonator. The problem of the frequency shift due to the resonator self heating with the optical power is solved thanks to a Pound-Drever feedback loop. A multifrequency RF filter is obtained, with a frequency step of 205 MHz between resonances, and a 3-dB bandwidth of 2.4 MHz. This corresponds to the computed optical resonator 3-dB bandwidth, and thus represents an efficient technique for the measurement of ultrahigh Q optical resonators. In the field of microwave applications, the equivalent Q -factor obtained is particularly interesting in the upper microwave range.     

Polymer micro-ring filters and modulators

Micro-ring wavelength filters and resonant modulators using polymer materials at 1300 nm and 1550 nm are analyzed, designed, and demonstrated. The rings are integrated with vertically coupled input and output waveguides. The devices are fabricated using optical lithography. Filters with a finesse of 141 and free spectral range of 5 nm at 1300 nm and finesse of 117 with a free spectral range (FSR) of 8 nm at 1550 nm are demonstrated. Ring resonators with a Q as high as 1.3 /spl times/ 10/sup 5/ at 1300 nm are demonstrated. The filters can be temperature tuned at the rate of 14 GHz//spl deg/C. Resonant ring modulators, which use an electrooptic polymer, are demonstrated. The resonance wavelength voltage tunes at the rate of 0.82 GHz/V. The modulators have a bandwidth larger than 2 GHz. Using the resonant modulator, and open eye diagram at 1 Gb/s is demonstrated.     

Narrow-band resonant optical reflectors and resonant optical transformers for laser stabilization and wavelength division multiplexing

We propose a new way of making highly resonant integrated optical circuits based on weak side-by-side coupling between waveguides and highQdistributed Bragg resonators. This method can be used to design a resonant optical reflector which, when used as a feedback element to a laser, will result in a compact structure that has both extremely narrow line width and very low chirp. By coupling the resonator to two waveguides, one on either side, an optical analog of the resonant transformer can be made. This device can be used for wavelength division multiplexing. Such multiplexer elements will both resonantly transform optical power from the laser to a common output channel and also provide feedback which locks the laser to the channel wavelength.     

Radiation from Bends in Dielectric Rod Transmission Lines

The radiation from the fundamental mode propagating around curved dielectric rod transmission lines is investigated experimentally with microwave frequencies. Three methods are used to determine the attenuation by radiation: measuring the insertion loss of bends, measuring the Q-factor of ring resonators, and measuring the Q-factor of sections of curved dielectric rod transmission lines terminated by large reflecting plates. The attenuation is found to depend mainly on the combination R lambda/sub 0//sup 2/ / r/sub 0//sup 3/ where R is the radius of curvature, lambda/sub 0/ the free space wavelength and r/sub 0/ a measure of the transverse field extent of the HE/sub 11/ mode. The experimental results are compared with theoretical predictions of other authors. The measured values of the attenuation constant are found to be smaller than the theoretical values. The distribution of the electromagnetic field near bends is recorded using a semiautomatic field plotter. From the field pictures, it can be concluded that the curved dielectric waveguide radiates tangentially from the outer side. The results presented will also be useful for understanding the mechanism of radiation from bent optical waveguides.     

Measurement of optical nonlinearity in silicon rich nitride waveguide ring resonators

The optical nonlinearities of amorphous silicon rich nitride corresponding to /spl chi//sup (3)/ in a static electric field have been measured by tracking wavelength shifts in the resonances of optical waveguide ring resonators as a function of an applied electrical field. The magnitude of the nonlinearity measured agrees well with expected values.     

Spectral characteristics of coupled-waveguide Fabry-Perotresonators and filters

Conventional Fabry-Perot resonators provide a narrow spectral width but lack the capability of longitudinal mode discrimination. A coupled-waveguide Fabry-Perot structure made of two parallel waveguides with reflecting mirrors at the ends is proposed for applications as mode selective resonator in single-mode diode lasers and as narrow-band wavelength filters. The interference of counter propagating waves from reflection by end mirrors and the coupling of waves between the two parallel waveguides contribute to the operation of this resonator structure. Thus, the device exhibits the attributes of both Fabry-Perot resonator and directional coupler. The coupled-mode theory of parallel waveguides is employed to analyze the structure. Both cases of identical and unidentical waveguides are examined. Resonance conditions and spectral characteristics are determined. It is shown that the coupled-waveguide Fabry-Perot resonator provides significant improvement in mode discrimination capability and longitudinal mode spacing over the conventional Fabry-Perot resonator     

Wavelength switching and routing using absorption and resonance

A resonator side coupled to a pair of waveguides can switch an optical signal between two ports by means of absorption. The absorptive mechanism is used to suppress the resonant power transfer, rather than to promote loss. Thus, the input signal only suffers small attenuation, provided that the mode volumes of the resonators can be made small enough. Multiply-coupled resonators lead to improved crosstalk performance for both the ON and OFF switched states. The performance of such devices are analyzed analytically, and universal switching curves are derived     

New methodology to evaluate the performance of ring resonators using optical low-coherence reflectometry

This paper describes the efficient implementation of optical low-coherence reflectometry (OLCR) measurements to evaluate the performance of InP-based high-index contrast ring resonators. Using examples of racetrack ring resonators, this paper shows here for the first time that all characteristic parameters relevant to resonator design (coupling coefficient k, propagation losses a, and optical cavity length L), and ultimately its performance, can be extracted in a straightforward manner. This is accomplished by introducing a new methodology that implicates OLCR measurements in transmission and also reflection modes as an alternative approach, in comparison with conventional spectral analysis, to extract resonator design parameters.