Time and spectral domain properties of distributed-feedback-type gain-clamped semiconductor optical amplifiers

A comprehensive model for the analysis of distributed-feedback (DFB)-type semiconductor optical amplifiers (SOAs) both in time- and frequency-domain is developed by combination of a wideband field-based traveling-wave rate equation model and an extended transfer matrix formalism for corrugated structures derived in spectral domain. The numerical implementation of the model is successfully fulfilled by dividing the device into many short segments along the cavity length. Based on this unique model, some time- and spectral-domain properties, such as amplified spontaneous emission, laser action, and signal amplification of DFB-type gain-clamped SOAs are simulated and analyzed.     

Photonic crystal-based circulators with three and four ports for sub-terahertz region

Three- and four-port circulators based on resonators in 2D photonic crystals with square unit cell possessing a low symmetry are investigated. The three-ports are described by only one specific element named antiplane of symmetry. On the other hand, the four-port circulators formed by cascading these two three-ports can have one of the two symmetries. One of them is described by the antiplane of symmetry, and the other symmetry corresponds to a twofold rotational axis. The theoretical part of our paper concerns scattering matrix analysis of the devices with different symmetries and also the operation of the four-port circulator as a single-pole triple-throw switch. Finally, the calculated frequency responses of two circulators are presented.     

Proposed interferometric optical isolator

This correspondence describes the concept of a non-reciprocal transmission isolator or four-port circulator consisting of an anisotropic index of refraction element inside the perimeter of a traveling-wave (ring) interferometer. The potential advantages of this device with regard to feedback power rejection capability and rejection ratio are discussed.     

Superconductive Traveling-Wave Photodetectors: Fundamentals and Optical Propagation

This paper studies the theory of superconductive traveling-wave photodector devices (STWPDs), as a general platform for ultrafast, ultrasensitive, and ultralow-noise optoelectronic functions such as detection, modulation, photomixing, high-frequency electrical signal generation and amplification. Principles of operation of STWPDs are discussed based on the kinetic-inductance theory of superconductive thin films and a thorough investigation of the guiding mechanism of light within this class of devices is presented. The transfer matrix method is introduced to model the superconductive optical waveguide in TWDs and an efficient numerical method based on the Cauchy integral method and the argument principle method are developed for the analysis and design of the waveguides. Moreover, several regimes of device operation will be distinguished in terms of the modal characteristics of the optical waveguide and their effects on the overall performance of the device will be highlighted.     

A novel method for measuring complex reflection coefficient using a four-port reflectometer

A novel method for precise measurement of complex reflection coefficient using a four-port reflectometer is presented. First, three new complex system constants are introduced, which depend only on the scattering parameters of the four-port reflectometer. Therefore, the stability of the reflectometer is greatly improved. Then, these complex system constants are used to determine the complex reflection coefficient T of the device under test by calibrating the reflectometer. Finally, a four-port reflectometer comprising a magic tee and a power detector is constructed and excellent experimental results are obtained.     

Optical devices from AlGaAs-GaAs HBTs heavily doped with amphotericSi

A new optoelectronic multifunctional device, having triple function of light emission, detection and amplification have been developed and some preliminary integrated circuits are demonstrated. The devices consist of N-p-n or N-P-n AlGaAs-GaAs HBT utilizing amphoteric Si heavily-doped GaAs or AlGaAs p-type base layer. Maximum current gain of 3600, and light output power of about 0.17 μW with 100 μA base current (I_b) in transistor mode operation and of about 10 μW with I_b=40 mA in diode mode operation are obtained. The optical emission wavelengths in both are about 0.85-0.86 μm. Optical gain of about 130 was obtained near the 0.86 μm wavelength as a detection transistor. Spectrum matching between emission and detection wavelength range is achieved. Some monolithic integrated circuits constituted of the transistors are proposed and demonstrated successfully. The relationship between current gain and radiative quantum efficiency at the transistor operation is also discussed     

Conservation Laws for Distributed Four-Ports (Short Papers)

Condition of reciprocity, Iosslessness, bilateral symmetry, transversal symmetry, and semireciprocity is given for a four-port in terms of its impedance, admittance, scattering, and transfer representation. Corresponding conditions are also presented for the system coupling matrix of a uniform distributed circuit. The results are applied to an anisotropic stratified waveguide.     

Analytical modeling and design criteria for traveling-wave FETamplifiers

The theoretical modeling and design of a traveling-wave FET are described. The device shows the capability of wide-bandwidth performance and high gain and could be useful in power applications. The proposed analytical model considers the full mode effects of the three-coupled transmission lines and an accurate analysis of the FET model in the traveling-wave amplifier. Starting from electrode dimensions and active zone doping, such a model allows one to calculate the scattering parameters. Thus, it is possible to analyze the device as a six port network in a circuit analysis program     

Gain saturation in traveling-wave ridge waveguide semiconductor laser amplifiers

The saturation behavior of traveling-wave ridge waveguide diode amplifiers is studied both numerically and analytically. It is shown that an 'effective saturation power' can be used to characterize the saturation of these devices by up to 4 dB. The effective saturation power, which is sensitive to device geometry, carrier density, and operating wavelength, is useful in the design of the ridge waveguide optical amplifiers.<>     

Cavity-Enhanced IR Absorption in Planar Chalcogenide Glass Microdisk Resonators: Experiment and Analysis

Planar microdisk optical resonators fabricated from Ge₂₃Sb₇S₇₀ chalcogenide glass on a silicon substrate are applied for cavity-enhanced spectroscopic measurement of chemical molecular absorption fingerprint. A 0.02 cm^{- 1} detection limit for these devices is demonstrated. This detection limit represents a threefold improvement as compared to a straight waveguide sensor, while the physical device length is reduced by 40-fold. The reduction in device footprint with enhanced sensitivity makes the structure attractive for ldquosensor-on-a-chiprdquo device applications. We also present a design optimization approach for cavity-enhanced IR absorption spectroscopy using traveling-wave resonators, which indicates that further performance improvement can be achieved in optimally coupled, low-loss resonant cavities.     

Integrated optical circular grating tap power divider

A new compact integrated optical tap and multiport power divider is provided. A four-port device is made using a glass substrate and is tested at 514 nm wavelength.<>     

Characteristics of a single-frequency Michelson-type He-Ne gas laser

A new mode suppression configuration is described for producing a single-frequency output from gaseous lasers. This configuration has the form of a modified Michelson interferometer where the basic modification is in the introduction of a third feedback mirror for coupling the two branches of the Michelson. Small path length differences between the two branches of the Michelson are responsible for the mode suppression properties of the device which come about through interference phenomena at the beam splitter. This results in a frequency-dependent power loss out of the beam splitter which can provide for large amounts of mode discrimination. The device is made into an oscillator by introducing gain into each of the two branches of the Michelson. A detailed analysis of the device is given based on the scattering matrix formalism. The results of the analysis give the oscillation frequencies, the degree of mode discrimination, the internal laser radiation intensity, and equations for the output power. Experimentally, a 10 mW single-mode 6328 Å He-Ne Michelson-type gas laser is described. Data on the frequency spectrum, output power, and amplitude stability of a free running laser are given and correlated with theory. While it is shown that single-frequency operation is easily obtained, the device in its present form does not include a means for stabilizing the frequency.     

Optimization of a polymer four-port microring optical router with three channel wavelengths

Optimization and simulation are performed for a polymer four-port microring optical router with three channel wavelengths, which contains four-group basic routing elements with two different ring radii. In terms of microring resonance theory, coupled mode theory and transfer matrix method, expressions of output power of basic routing element and optical router are derived. In order to realize single-mode propagation, low optical transmission loss and phase match between microring waveguide and channel waveguide, the device parameters are optimized. With the selected three channel wavelengths of 1550 nm, 1552 nm and 1554 nm, characteristics are calculated and analyzed, including output spectrum, insertion loss and crosstalk. Simulation results indicate that the device has 12 possible I/O routing paths, the insertion losses of three channel wavelengths along their routing paths are within the range of 0.02-0.61 dB, the maximum crosstalk between the on-port along each routing path and other off-ports is less than -39 dB, and the device footprint size is -0.13 mm^2. Based on the proposed structure, through proper selection on ring radius, the routing structure can also be used for other channel wavelengths. Therefore, the designed structure shows wide applications in integrated optical networks-on-chip （NoC）.     

A comparison of power requirements of traveling-wave LiNbO3optical couplers and inteferometric modulators

It is shown that a coupler and interferometer may be considered two extremes of a generalized two-guide coupler device in which electrode length is less than a coupling length. For electrode lengths less than half of a coupling length, the generalized device looks more like an interferometer than a coupler. The impedance and electrical loss of asymmetric-stripe and coplanar-waveguide transmission lines on LiNbO3for thick as well as thin electrodes are then presented. The effects of the electrical loss on the bandwidth and drive requirements of traveling-wave LiNbO3couplers and interferometric devices are discussed, and it is shown that electrical loss in the transmission line is more detrimental to a coupler than to an interferometer. These results are then used to compare the drive power requirements of coupler and interferometric devices, and it is shown that for the same bandwidth and same optical guide dimensions, an interferometric device with a coplanar transmission line can require a lower drive power than a coupler with an asymmetric-stripe line.     

A flexible design procedure for microstrip planar disk 3 dBquadrature hybrids

A flexible design procedure is presented for the recently synthesized microstrip planar disk 3-dB quadrature hybrid. The design approach adopted uses external two-port matching networks connected at each of the device coupling ports. It is shown that a four-port device having a given disk radius and the necessary hybrid symmetry can be designed to operate as a 3-dB quadrature hybrid over a wide range of frequencies simply by an appropriate positioning of the coupling ports and an appropriate choice of matching network. The design procedure has been verified experimentally by the successful synthesis of two new 3-dB quadrature hybrid devices     

Four-port scattering matrix for dual-polarized wave transmissionand reflection network

Co-directional and bi-directional, co-polarized and cross-polarized characteristics of a lossless, matched four-port transmission network have been examined. For example, an arbitrary-inclined dielectric plate in a circular or square waveguide supporting dual-orthogonal linearly polarized modes has been analyzed, and a coordinate system is defined to apply for co-directional and bi-directional propagating circularly polarized waves. The matrix elements are polarization state and network dependent. Instead of using the terms network reciprocity and matrix symmetry, the matrix elements are discussed in terms of ratios to describe co-directional, bi-directional, co-polarized, cross-polarized, and polarization discrimination properties. Some of the ratios are equal to 1∠0° and others 1∠180°. Applications of this analysis are described. If the properties of the four-port network are frequency dependent and integrated over a bandwidth, and/or time dependent and integrated temporally, the scattering matrix formulation is not valid due to the presence of a randomly polarized component; in these cases a Mueller matrix is used to characterize the network     

Coupled-mode analysis of an electrooptic frequency shifter

In this paper, we present a semiclassical wave equation analysis using a coupled-mode expansion formalism to study the effect of a microwave field on a train of short optical pulses co-propagating in a traveling-wave modulator structure. This device can continuously shift the central frequency of light pulses. We demonstrate the effect of the applied field on the light spectrum, the dependence on the relation between microwave wavelength and pulse length, and the effect of changing the interaction length or the power of the applied microwave field. The results of the calculation of these effects are presented.     

A Rigorous Technique for Measuring the Scattering Matrix of a Multiport Device with a 2-Port Network Analyzer

A new measurement technique is described that eliminates the mismatched-induced errors that occur when the scattering matrix of a multiport device is measured with a 2-port network analyzer. These errors arise from neglecting the finite reflections from the imperfect auxiliary loads terminating the unused ports of the device under test in each of the required 2-port measurements. It is shown how a systematic application of the generalized scattering matrix renormalization transform completely eliminates these errors. This new method is completely general and can therefore be applied to measurements of the scattering matrix of an n-port device with an m-port network analyzer (m相似文献   

Theoretical analysis of resonant waveguide optical second harmonicgeneration devices

Theoretical analysis of resonant waveguide SHG devices is presented. Mathematical expressions for SHG interaction in waveguides for arbitrary initial conditions were derived and applied to the analysis. Dependences of SHG efficiency on pump amplitude of singly and doubly resonant devices with various cavity mirror reflectivities, phase-mismatch, and propagation losses are compared with that of traveling-wave devices. It is shown that in resonant SHG devices much higher efficiency is obtained for low pumping power than in traveling-wave device. It is found, for the first time, that complete conversion can be attained for a finite input power in the doubly resonant devices. However, the efficiency is very sensitive to the propagation losses     

Microstrip-Slot Coupler Design-Part I: S-Parameters of Uncompensated and Compensated Couplers

Using the even-odd mode analysis of four-port networks with double symmetry, the scattering parameters of the microstrip-slot coupler are derived from the even- and odd-mode parameters of the coupler cross section. The uncompensated coupler and the coupler compensated by extending the slot fines are treated and design specifications are given covering the compensation slot lines. A comparison with experimental data will be given in Part II.