Showing papers in "IEEE Journal of Quantum Electronics in 1977"
TL;DR: In this article, the theory and device applications of periodic thin-film waveguides are discussed, including mode solutions, optical filters, distributed feedback lasers, distributed Bragg reflector (DBR) lasers, grating couplers, and phase matching in nonlinear interactions.
Abstract: This paper deals with the theory and device applications of periodic thin-film waveguides. Topics treated include mode solutions, optical filters, distributed feedback lasers (DFB), distributed Bragg reflector (DBR) lasers, grating couplers, and phase matching in nonlinear interactions.
370 citations
TL;DR: In this paper, the authors extended the coupled mode equations to include radiation and other partial wave coupling effects in distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers, as well as orthogonal radiating couplers.
Abstract: The familiar coupled mode equations are extended in a self-consistent fashion to include radiation and other partial wave coupling effects in distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers, as well as orthogonal radiating couplers. This general formulation takes into account the joint interaction of the two coherent contradirectional guided waves with arbitrarily shaped gratings. In addition to the modified coupled mode equations, which contain added constants characterizing the interactions, expressions for radiated waves are also obtained. A particular waveguide geometry is studied in detail. The interaction constants are evaluated for all Bragg orders up to the fourth and various blazing angles. Then the equations are solved for both a DBR and DFB laser. In the former case it is shown that the reflection is smaller than that computed without the interaction constants. Furthermore, reflection is asymmetrical relative to the Bragg condition. The DFB laser is shown to have an asymmetrical longitudinal mode structure even for symmetrical boundary conditions and to have only slightly higher thresholds than previously calculated.
224 citations
TL;DR: In this article, an expression for the power transferred out of the lowest order mode was obtained for a parabolic-shaped horn, which demonstrates that long structures will be needed to maintain adiabatic operation.
Abstract: Mode coupling in optical waveguide horns is described in detail. Analytic approximations for the coupling constant and phase difference are derived. For a parabolic-shaped horn an expression for the power transferred out of the lowest order mode is obtained, which demonstrates that long structures will be needed to maintain adiabatic operation.
170 citations
TL;DR: In this paper, the optical wave of wide-stripe lasers is found to be guided by changes in the real part of the dielectric constant that are caused by a dip in carrier concentration along the axis of the lasing filament.
Abstract: Experimental measurements of the optical-beam parameters of conventional oxide-insulated GaAs stripe-geometry lasers as a function of stripe width have shown a marked difference in the waveguide mechanism of narrow-stripe ( \simeq10 \mu m) and wide-stripe ( >20 \mu m) lasers. The optical wave of narrow-stripe lasers is guided by the previously reported gain-guiding mechanism. The optical wave of wide-stripe lasers is found to be guided by changes in the real part of the dielectric constant that are caused by a dip in carrier concentration along the axis of the lasing filament. This self-focused guiding has been predicted theoretically. These experimental results strongly support the hypothesis that in all cases the waveguides are formed predominantly by the naturally occurring variations in carrier concentration beneath the stripe. A new and fairly comprehensive mathematical model has been developed based on this assumption. The model predicts the carrier concentration, resultant gain, and dielectric constant profiles together with the optical-beam parameters and light/current characteristics of stripe-geometry lasers. The model is applicable over a wide range of stripe widths and device structures. The results are compared with experiment over the range of stripe widths from 10-20 \mu m and found in reasonable agreement. The effects of narrowing the stripe width below 10 μm are calculated and found to be in qualitative agreement with recently published experimental results. In particular the light-output power at which a predicted "kink" in the light/current characteristic occurs is found to increase rapidly as the stripe width reduces.
169 citations
TL;DR: In this paper, a detailed study has been carried out on the propagation-mode characteristics of graded-index planar optical waveguides formed by silver-sodium ion exchange, and it has been found that the index profile can be accurately modeled by a monotonic decrease from a maximum value at the surface, following a second-order polynomial distribution.
Abstract: A detailed study has been carried out on the propagation-mode characteristics of graded-index planar optical waveguides formed by silver-sodium ion exchange. It has been found that the index profile can be accurately modeled by a monotonic decrease from a maximum value at the surface, following a second-order polynomial distribution. Definition of an effective diffusion constant leads to a universal mode-dispersion diagram applicable over a wide range of fabrication conditions. Interferometric observations of the refractive-index profile, together with electron microprobe analysis, give further support to the second-order polynomial distribution. The index profile has also been compared with silver-concentration profiles predicted by interdiffusion theory. Results obtained are also relevant to methods of coupling between planar and circular fiber-optical waveguides, where sections of optical fiber undergo ion exchange.
165 citations
TL;DR: In this article, the rate of absorption and emission of radiation is calculated for two laser fields interacting with a homogeneously broadened, three-level molecular system using the time-dependent Schrodinger equation.
Abstract: The rate of absorption and emission of radiation is calculated for two laser fields interacting with a homogeneously broadened, three-level molecular system. The time-dependent Schrodinger equation is used in the density matrix formalism and the laser fields are treated classically. The laser fields, at frequencies ω p and ω s , are off resonance by δ p and δ s , respectively, such that |\delta_{p}|, |\delta_{s}| \ll \omega_{p}, \omega_{s} . Analytic expressions are derived for the imaginary part of the electric susceptibility, \chi"(\omega_{p}) and \chi"(\omega_{s}) . The present work differs from previous calculations in that the laser fields may have arbitrary values of field strength and each field may be on or off resonance. A discussion is presented of the properties of the solutions for \chi"(\omega_{p}) and \chi"(\omega_{s}) , for both strong and weak laser fields, based on computer evaluation of the general analytic expressions. It is shown that the solutions may be divided into single-photon and two-photon, or Raman, contributions. Conditions for optimizing dI(\omega_{s})/dz and the photon conversion efficiency are derived. These results may be applied to analyzing the pulsed, optically pumped submillimeter laser and to studying two-photon absorption in a gas.
140 citations
TL;DR: In this paper, the authors measured the magnitude and spatial distribution of optical gain in a stripe-geometry junction laser and found that the width of the fundamental mode is in excellent agreement with a two-dimensional waveguide in which confinement along the junction plane is induced primarily by the optical gain profile.
Abstract: Measurements of the magnitude and spatial distribution of the optical gain in a stripe-geometry junction laser are related to observations of the intensity profile along the junction plane of the same laser. We find that the width of the fundamental mode is in excellent agreement with a two-dimensional waveguide in which confinement along the junction plane is induced primarily by the optical-gain profile. The remainder of the confinement is consistent with a refractive-index profile established by a temperature distribution in the presence of defocusing by the free carriers. Within the two-dimensional model, we find no evidence of defocusing like that deduced previously for double-heterostructure lasers.
118 citations
TL;DR: In this paper, changes occuring in selected optical properties of double-heterostructure junction (AlGa) laser during the initial stage of accelerated aging are reported, including the current dependence of the lasing emission and the orthogonally polarized (nonlasing) emission, the symmetry of the emission with respect to the two output faces, the time stability of the light intensity, and the frequency of the internal laser resonance.
Abstract: Changes occuring in selected optical properties of CW (AlGa)As double-heterostructure junction lasers during the initial stage of accelerated aging are reported. The characteristics selected for investigation are relevant to the operation of the laser in an optical communication system and include the current dependence of the lasing emission and the orthogonally polarized (nonlasing) emission, the symmetry of the emission with respect to the two output faces, the time stability of the light intensity, and the frequency of the internal laser resonance. In spite of the variability among the aging behaviors of individual lasers, characteristic changes did emerge as statistically significant. For example, a substantial decrease in the emission symmetry was commonly observed. A second important effect was the creation of a self-induced intensity pulsation, at a frequency typically between 300 and 600 MHz, in lasers which initially exhibited no intensity modulation. A statistical analysis of the data was made to correlate these instabilities with asymmetries in the lasing or nonlasing emission and/or changes in the emission symmetry. No evidence was found to support previously published conjectures that the pulsations are caused by the formation of dark-line defects or by axial nonuniformities in the pumping current.
107 citations
TL;DR: A traveling-wave electrooptic phase modulator using a Ti-in-diffused LiNbO 3 optical waveguide was designed and constructed with emphasis placed on broad-band operation.
Abstract: A traveling-wave electrooptic phase modulator using a Ti-in-diffused LiNbO 3 optical waveguide was designed and constructed with emphasis placed on broad-band operation. As a microwave waveguide, a coplanar parallel stripline of aluminum with characteristic impedance of 48 Ω was fabricated on the crystal surface. The electrodes are 1.5 μm thick, 1 cm long, and 60 μm apart. The modulator was tested at 0.63 μm over a bandwidth of 7.5 GHz. For 250-mW drive power, the measured phase-modulation index was 1 rad up to about 3 GHz and reduced to 0.5 tad at 7.5 GHz.
103 citations
TL;DR: In this paper, the light intensity fluctuations in each longitudinal mode of CW AlGaAs-GaAs stripe-geometry double-heterostructure junction lasers which oscillate in many modes are investigated experimentally, when the operating current is within a few tens of percent above threshold.
Abstract: The light-intensity fluctuations in each longitudinal mode of CW AlGaAs-GaAs stripe-geometry double-heterostructure junction lasers which oscillate in many modes are investigated experimentally, when the operating current is within a few tens of percent above threshold. In addition, experimental results about the noise characteristics for the lasers directly modulated are discussed in relation to the lasing-spectrum broadening. The total intensity output can be well stabilized at currents above threshold by larger than 10 percent, even when the same laser is modulated by large pulse currents at such high speeds as 400 Mbits. However, the relative noise power for each mode is about 30 dB larger than that for total modes within the whole frequency region observed in this work, and the noise spectrum becomes essentially flat when the laser is modulated. The relative fluctuations for each mode of the modulated laser seems to be nearly equal to the low-frequency fluctuations in each mode without modulation for a given normalized pump rate.
92 citations
TL;DR: In this paper, an interactive kinetic model for bound-free excimer lasers is described, with particular emphasis on the electron beam pumped rare gas systems, and the interaction of the photon field with excited states is examined in detail.
Abstract: An interactive kinetic model for bound-free excimer lasers is described, with particular emphasis on the electron beam pumped rare gas systems. Important kinetic processes and the interaction of the photon field with excited states are examined in detail. Application of the model to the xenon and krypton oscillators yields results which are in good agreement with experimentally observed quantities. It is found that the collisional coupling of the excimer singlet and triplet manifolds in combination with the losses arising from photoionization play an important role in determining the performance. Numerical values of the parameters used in the computational model are given.
TL;DR: In this article, the active region gain expression for Pb 1-x Sn x Te lasers is obtained from the k \cdot p model of the conduction and valence band extrema.
Abstract: The active region gain expression for Pb 1-x Sn x Te lasers is obtained from the k \cdot p model of the conduction and valence band extrema. Curves of gain versus frequency with current, temperature, and majority carrier concentration as parameters are calculated using published values of the k \cdot p model parameters. In addition, threshold current versus temperature and threshold current versus majority carrier concentration curves are given. A simple expression is obtained for the conductivity effective mass for use in the equation for free-carrier absorption appropriate to the highly degenerate majority carrier concentrations typical of Pb 1-x Sn x Te laser material.
TL;DR: In this article, the behavior of the chirped gratings with variable periods (chirped grasps) was analyzed as a function of wavelength, angle between the illuminating beams, the F number of the lens, and its position.
Abstract: Gratings with variable periods (chirped gratings) have been fabricated by recording the interference pattern of a collimated laser beam with a converging beam generated by a cylindrical lens. An analysis is presented for the behavior of the chirped gratings as a function of wavelength, the angle between the illuminating beams, the F number of the lens, and its position. To calculate the power radiated into air, the coupled-mode equations are solved for the case of a waveguide with chirped surface corrugation. Experimentally, chirped gratings have been etched on the surface of an optical waveguide and used to couple light out of the waveguide. It was found that the light was focused outside the waveguide, and the fraction of the power radiated into air compared favorably with the theoretical calculation. The focal point outside the waveguide was found to move by about 1 cm when the wavelength was changed by 500 A-in agreement with theoretical estimates.
TL;DR: In this article, the authors proposed a scalable Q-switched Nd; YAG laser with a 2 percent wall-plug efficiency for high-power nonlinear processes with phase-match stability and thermal profile.
Abstract: repetitively Q-switched Nd; YAG laser. The pulsewidth was 150 ns. Current data indicate that such a system is scalable to 300 W of 0.53 pm output with a 2percent wall-plug efficiency. These solutions to power-handling problems that have limited the applications of FD can be extended to other high-power nonlinear processes where phase-match stability and thermal profile present a problem. The result will be new sources for many laser applications.
TL;DR: In this article, a forced mode-locked dye laser system capable of ultra-short pulse formation is examined experimentally, and the magnitudes and relative timing of the dye pulse, the pumping pulse and the fluorescence are measured.
Abstract: A forced mode locked dye laser system capable of ultra-short pulse formation is examined experimentally, and the magnitudes and relative timing of the dye pulse, the pumping pulse, and the fluorescence are measured. Significant fast inversion loss of the gain medium is noted, and, for normal mode locked operation, only one pulse is observed to circulate in the cavity. A simplified model of the operation of the dye laser, based on a recent theory by Haus, is presented, and is seen to reproduce the main features of the experiment.
TL;DR: In this paper, a highly efficient TE-TM mode conversion device utilizing the acoustooptic effect has been demonstrated, where an acoustic surface wave propagating collinearly with an optical guided wave has been made by an acoustic receiver.
Abstract: A highly efficient TE-TM mode conversion device utilizing the acoustooptic effect has been demonstrated. Mode conversion has been made by an acoustic surface wave propagating collinearly with an optical guided wave. The maximum mode conversion, although the fraction was restricted to 70 percent, has been obtained with an acoustic power of only 55 mW (electrical input 0.55 W). Effective interaction length of the present device is limited to 5 mm due to optical and/or acoustic inhomogeneity of the waveguides. For selecting TE and TM waves, a polarizer is constructed monolithically and the extinction ratio is improved by up to 21 dB. Performance characteristics of a tunable optical filter of this type of the mode conversion are also discussed.
TL;DR: In this article, the performance of dye lasers with excited singlet-state absorption (ESA) at the pump and the lasing wavelengths is analyzed for short pulse pumped systems in the medium range of pumping intensities.
Abstract: The performance of dye lasers with excited singlet-state absorption (ESA) at the pump and the lasing wavelengths is analyzed for short pulse pumped systems in the medium range of pumping intensities. Analytical and numerical solutions are presented for a wide range of the variable parameters such as ESA cross sections, the cavity reflectivity, and the pumping intensity. An experiment is described for measuring ESA cross sections in the pumping as well as the lasing regions, and the results for rhodamine 6G and rhodamine B are given, showing that due to ESA, the effective gain of the laser will be much lower than that expected from previously published data on the stimulated emission cross sections.
TL;DR: A number of far-infrared laser emission lines from CH 3 OH, pumped by a CO 2 laser, have been assigned to specific energy levels of the rotation-internal rotation spectrum in the first excited CO stretch state as mentioned in this paper.
Abstract: A number of far-infrared laser emission lines from CH 3 OH, pumped by a CO 2 laser, have been assigned to specific energy levels of the rotation-internal rotation spectrum in the first excited CO stretch state. The assignments are based on comparison with the established model for the vibrational ground state, and on criteria concerning internal consistency, polarization, and line strength.
TL;DR: In this article, experimental determination of the spontaneous emission factor of an injection laser is presented, which is in good agreement with the theoretical prediction based upon the classical wave theory, which shows that the damping oscillation can be decreased in a laser consisting of very small active region.
Abstract: In this paper, experimental determination of the spontaneous-emission factor of an injection laser is presented. For a lot of conventional AlGaAs DH stripe lasers, spontaneous-emission factors of about 10-5were obtained from the measurement of the light intensity of a lasing mode versus the injected current. These values are in good agreement with the theoretical prediction based upon the classical wave theory. Brief discussion of the magnitude of the spontaneous-emission factor is given relating to the direct modulation characteristics of a semiconductor laser, which shows that the damping oscillation can be decreased in a laser consisting of very small active region.
TL;DR: In this paper, experimental studies of an amplitude modulator using Ti-diffused LiNbO 3 branched waveguides have been conducted and the authors present experimental evidence in support of three problem areas connected with the improvement of performance of the device.
Abstract: We report here experimental studies of an amplitude modulator using Ti-diffused LiNbO 3 branched waveguides. In this paper we present experimental evidence in support of three problem areas connected with the improvement of performance of the device. Solution of the problems has involved the development of a new in-diffusion process to eliminate any background radiation, introduction of a new electrode arrangement which consists of extra electrodes at the branching section to control the splitting action, and finally performing measurements at a longer wavelength ( \lambda_{0} = 1.15 \mu ) to overcome the limitations of available photomasks.
TL;DR: In this article, a wide-band real-time spectrum analyzer is examined as a viable integrated optical circuit for processing electronic signals, which includes a Luneburg beam expansion lens system, a surface elasto-optic Bragg spatial modulator, reflectors, and a waveguide coupled photodetector array, all formed on thermally grown SiO 2 on Si as the substrate.
Abstract: A wide-band real-time spectrum analyzer is examined as a viable integrated optical circuit for processing electronic signals. The spectrum analyzer includes a Luneburg beam expansion lens system, a surface elastooptic Bragg spatial modulator, reflectors, a Luneburg Fourier-transform lens, and a waveguide coupled photodetector array, all formed on thermally grown SiO 2 on Si as the substrate. A distributed-feedback (GaAl)As laser with hybrid coupling is included as the carrier for the optical Fourier transform. The developmental status of this integrated-optical spectrum analyzer and its essential design considerations are delineated.
TL;DR: In this paper, the dynamics of (dipole-dipoles) laser induced collision processes are studied, and transition probability and collision cross section are given as a function of the detuning from the R = \infty frequency of the separated atoms, and of the incident laser power density.
Abstract: This paper studies the dynamics of (dipole-dipole) laser induced collision processes. Coupled equations are numerically integrated, first over time, and then over impact parameter. Transition probability and collision cross section are given as a function of the detuning from the R = \infty frequency of the separated atoms, and of the incident laser power density. Numerical results are compared with approximate formulae for collision cross section at line center and in the wing.
TL;DR: In this paper, a review is given on a variety of liquid-crystal optical switches or modulators and specific work is described on the analysis and experiment on thin-film nematic liquidcrystal guides with propagation constant controlled by means of an applied voltage across the films.
Abstract: Liquid-crystal optical waveguides may be modulated or switched with high sensitivity by electrooptic, magnetooptic or acoustooptic effects. Such guides, however, have relatively slow response times and relatively high scattering losses so that they currently appear limited to special-purpose applications. A review is given on a variety of liquid-crystal optical switches or modulators. Specific work is then described on the analysis and experiment on thin-film nematic liquid-crystal guides with propagation constant controlled by means of an applied voltage across the films. A dynamic scattering switch is also demonstrated. Recent results show switchable grating directions in films having mixtures of nematic and cholesteric liquid crystals. The controlling variable is the frequency of the applied electric field.
TL;DR: In this paper, the propagation constants, attenuation, and field distributions of dielectric waveguides clad by a thin metal layer are calculated, and it is shown that by reducing the metal thickness, the attenuation of optical modes reduces in such a way that short metal-clad devices become possible even in thin guides with thicknesses near cutoff.
Abstract: Propagation constants, attenuation, and field distributions of optical modes in dielectric waveguides clad by a thin metal layer are calculated. It is shown that by reducing the metal thickness, the attenuation of optical modes reduces in such a way that short metal-clad devices become possible even in thin guides with thicknesses near cutoff. As an application, a cutoff polarizer in symmetrical waveguides has been built by depositing a small thin silver stripe on the surface of the guide. By this structure the TE 0 mode is coupled out into the substrate, whereas the TM 0 mode is transmitted with very low losses. The best extinction ratio measured is 18 dB. The polarizer can be used as a TE 0 mode coupler into symmetrical waveguides as well.
TL;DR: In this paper, the authors measured the pressure dependence of absorption, absorption coefficients and detunings for CO 2 pump lines and the strong fat infrared emission in optically pumped D 2 O.
Abstract: Using the pressure dependence of absorption, absorption coefficients and detunings were measured for CO 2 pump lines and the strong fat infrared emission in optically pumped D 2 O. The P (32) CO 2 line was found to be detuned ∼1.5 GHz from the ν 2 band transitions 6_{6}, 6_{5} \rightarrow 5_{5}, 5_{4} . The resulting emission lines at 50.3 μm and 66 μm were found to be detuned from their respective transitions by about the same amount. On the basis of these measurements and gain estimates for the far infrared, the resulting emission lines are identified as stimulated Raman emission.
TL;DR: In this article, various materials, lens structures, and processes are examined relative to the lens requirements of an RF spectrum analyzer implemented through the use of an integrated-optics format, and it is concluded that a thin-film Luneburg lens is the most viable planar approach based upon the useof oxides and, when high refractive-index materials must be employed, the spherical depressed geodesic becomes a feasible alternate.
Abstract: Various materials, lens structures, and processes are examined relative to the lens requirements of an RF spectrum-analyzer implemented through the use of an integrated-optics format. Factors which distinguish optical-waveguide lenses and reflectors from conventional imaging lens systems are enumerated. It is concluded that a thin-film Luneburg lens is the most viable planar approach based upon the use of oxides and, when high refractive-index materials must be employed, the spherical depressed geodesic becomes a feasible alternate.
TL;DR: In this paper, the frequencies of 46 CW laser lines with wavelengths between 0.1 and 0.7 mm have been measured by heterodyne methods, with threshold pump powers of 3 W or less.
Abstract: The frequencies of 46 CW laser lines commonly used for submillimeter spectroscopy, with wavelengths between 0.1 and 0.7 mm, have been measured by heterodyne methods. All the fines are optically pumped by a CO 2 laser, with threshold pump powers of 3 W or less. The precision of measurement, limited by the laser linewidth, is typically ± 1 part per million.
TL;DR: In this paper, the distributed capacitance of the periodic grating, the 2- electrode, and the 3-electrode stripline waveguide modulators were derived exactly using conformal mapping techniques.
Abstract: The distributed capacitance of the periodic grating, the 2- electrode, and the 3-electrode stripline waveguide modulators are derived exactly using conformal mapping techniques The capacitance formulas are shown to have a common form; they differ in a single parameter which is simply related to the electrode width and spacing Discrepancies previously found in the capacitance expressions used for the 2-electrode structure are resolved For the finite 3-electrode structure studied here, a self- and a mutual distributed capacitance are defined Techniques for switching a 3-electrode directional coupler are suggested The closed form mapping function derived here will be useful in the design of waveguide directional couplers The electrode structures examined here are similar to those used in surface acoustic wave devices; therefore, the capacitance calculations should also be applicable
IBM1
TL;DR: An opaque document scanner as mentioned in this paper generates a locus of points from a stationary light beam on an opaque document and the same hologram or similar one mounted for conjoint movement collects light energy reflected from the document at each point and focuses this energy onto a stationary detector to provide electrical signals corresponding to the information scanned on the document.
Abstract: An opaque document scanner in which a moving hologram generates a locus of points from a stationary light beam on an opaque document and the same hologram or a similar one mounted for conjoint movement collects light energy reflected from the document at each point and focuses this energy onto a stationary detector to provide electrical signals corresponding to the information scanned on the document.
TL;DR: In this article, high-power far infrared (FIR) laser operation at the 10-100 mW level is described for wavelengths throughout the 40 μm-1.22 mm spectral region.
Abstract: High-power far infrared (FIR) laser operation at the 10- 100 mW level is described for wavelengths throughout the 40 μm-1.22 mm spectral region. These data correspond to order of magnitude improvements in converting CO 2 laser energy into FIR laser output. This improved FIR laser performance is attributed to a waveguide laser geometry with reduced losses for the CO 2 pump and also to a new method of output coupling. The basic design concept of the efficient laser resonator is discussed as well as the prospect for further increases in laser performance through improved efficiency and sealing.