Showing papers in "IEEE Journal of Quantum Electronics in 1972"
TL;DR: In this article, a method to compensate the astigmatic distortions introduced by both the internal mirror and the cell is described, which allows the formation of a tight intracavity focus as required in applications such as CW dye lasers.
Abstract: An analysis is given of folded 3-mirror laser resonators with an internal cell set at Brewster's angle. A method is described to compensate the astigmatic distortions introduced by both the internal mirror and the cell. This compensation is achieved for a specific relation between cell thickness and folding angle. It allows the formation of a tight intracavity focus as required in applications such as CW dye lasers. A discussion is given of the mode characteristics of compensated cavities and of the limitation on beam concentration set by the thickness of the Brewster cell.
430 citations
TL;DR: In this paper, the refractive indices of the ternary A^{I}B^{III}C_{2}^{VI} semiconductors CuAlSe 2, AgGaSe 2, CuGaSe2, and AgInSe 2 have been measured over most of the transparency range of these crystals.
Abstract: The refractive indices of the ternary A^{I}B^{III}C_{2}^{VI} semiconductors CuAlSe 2 , AgGaSe 2 , CuGaSe 2 , and AgInSe 2 have been measured over most of the transparency range of these crystals. The optical nonlinear coefficients for second-harmonic generation of AgGaSe 2 CuGaSe 2 , and AgInSe 2 have also been measured. Three-frequency colinear phase matching is analyzed in detail for AgGaSe 2 . The birefringences of the other three crystals are not sufficient to permit three-frequency colinear phase matching within the range of the measured index. The merits of AgGaSe 2 for nonlinear optical applications are evaluated in comparison with other promising infrared nonlinear materials.
353 citations
TL;DR: Reflectivity of a cleaved facet forming a laser cavity in a double heterostructure injection laser is analyzed on the basis of a dielectric waveguide model and the reflectivity of modes is numerically provided for a GaAs-AlGaAs double-heterostructured injection laser as mentioned in this paper.
Abstract: Reflectivity of a cleaved facet forming a laser cavity in a double heterostructure injection laser is analyzed on the basis of a dielectric waveguide model and the reflectivity of modes is numerically provided for a GaAs-AlGaAs double-heterostructure injection laser. The modes that distinguish field distributions perpendicular to a junction plane are considered up to the sixth order with TE and TM modes. The dependence of threshold conditions on the mode, the relations between the lowest threshold mode and the structures of the injection laser are studied. Provided mode reflectivity is solely responsible for modal selection, the single-mode operation is theoretically shown to be possible by choosing a suitable length of the cavity even though the thickness of the active layer is large.
283 citations
TL;DR: In this article, the EH 11 lowest order waveguide mode as a function of mirror position and mirror radius was analyzed and it was shown that some mirror positions and radii are optimum, in that they provide low coupling loss and are relatively insensitive to mirror position.
Abstract: Hollow waveguide gas lasers of the type described by Smith have some inherent loss in coupling radiation from the guide into free space and back into the guide. This paper calculates that loss for the EH 11 lowest order waveguide mode as a function of mirror position and mirror radius. It is shown that some mirror positions and radii are optimum, in that they provide low coupling loss and are relatively insensitive to mirror position.
220 citations
TL;DR: The sensitivity of a broad-band dye laser to selective intracavity absorption is proportional to the number of oscillating modes as discussed by the authors, which is obtained from a rate equation model, taking into account the spectral homogeneity, but spatial inhomogeneity of the laser saturation.
Abstract: The sensitivity of a broad-band dye laser to selective intracavity absorption is proportional to the number of oscillating modes. This result is obtained from a rate equation model, taking into account the spectral homogeneity, but spatial inhomogeneity of the laser saturation. An increase of absorption sensitivity by a factor of 105, compared to a single-pass measurement, is observed in an experiment with an iodine vapor absorption cell inside the cavity of a CW dye laser. The fluorescence of an external iodine vapor cell provides a convenient selective absorption monitor.
176 citations
TL;DR: In this article, the properties of the Nd-ultraphosphate NdP 5 O 14 (NdUP), a crystalline material that appears to be a promising candidate for an efficient Nd laser, are described.
Abstract: The properties of the Nd-ultraphosphate NdP 5 O 14 (NdUP), a crystalline material that appears to be a promising candidate for an efficient Nd laser, are described. The Nd concentration of 4.1021/cm3is ∼60 times higher than the upper limit useful for doped laser crystals ( \simI percent) like Nd:YAG. Despite the much higher Nd concentration the linewidths and cross sections of the major transitions are shown to be very similar to those of Nd:YAG. Therefore, it is expected that the gain per unit length in NdUP is also ∼60 times higher than in Nd:YAG. The crystal structure, the absorption and fluorescence spectra, level assignments, and various other features of NdUP are reported. Other rare earths form similar insoluble stable compounds. Most of them are transparent from the UV to the near IR except for the absorption bands of the metal ions.
173 citations
TL;DR: In this article, the refractive indices of ZnSiAs 2, CdGeP 2, and cdGeAs 2 have been determined over a wide range of wavelengths and the optical nonlinear coefficient for second-harmonic generation from the 10.6-μ CO 2 laser have been measured.
Abstract: The refractive indices of ZnSiAs 2 , CdGeP 2 , and CdGeAs 2 have been determined over a wide range of wavelengths and the optical nonlinear coefficient for second-harmonic generation from the 10.6-μ CO 2 laser have been measured. The absorption coefficient versus wavelength is given for the above materials as well as for ZnGeP 2 , a previously discussed material. Three-frequency phase-matched mixing is described for each material.
148 citations
TL;DR: In this article, a theoretical treatment of the fluctuation mechanism involved in the generation of picosecond laser pulses with saturable absorbers is presented, where the processes responsible for shortening of the pulsewidth and for selection of the most intense pulse are treated.
Abstract: This paper presents a theoretical treatment of the fluctuation mechanism involved in the generation of picosecond laser pulses with saturable absorbers. The processes responsible for the shortening of the pulsewidth and for selection of the most intense pulse are treated. Some experimental results that confirmed the treatment are presented. The influence of inertia of saturable absorber and nonlinear losses (self-focusing and self-modulation) is discussed.
136 citations
TL;DR: In this article, the linear and circular birefringent properties of low-loss single-mode glass fibers are found to depend upon length, and some anomalous behavior can be explained in terms of properties varying locally along the fiber and a resultant upper information rate of over 1012bits/s is estimated.
Abstract: The linear and circular birefringent properties of low-loss single-mode glass fibers are found to depend upon length. Depolarization is about 1 percent/km. Some anomalous behavior can be explained in terms of properties varying locally along the fiber and a resultant upper information rate of over 1012bits/s is estimated. Very small stress distributions or core ellipticities could give rise to the observed effects.
132 citations
TL;DR: In this paper, the authors discussed the probabilistic nature of the damaging interaction between light and matter and showed that there is some probability to induce damage at any level of optical irradiation, then the reported irreproducible damageresistance properties of many useful materials can be understood.
Abstract: This paper discusses the probabilistic nature of the damaging interaction between light and matter. It is shown that when one recognizes that there is some probability to induce damage at any level of optical irradiation, then the reported irreproducible damage-resistance properties of many useful materials can be understood. This point of view also explains why some optical components may be safely irradiated many times before damage occurs, though no other change in the material can be detected prior to the observation of damage. Experimental data showing the probability for surface damage as a function of power density are presented for several materials. The dependence of damage probability on optical field strength is similar to that of the dc ionization coefficients for semiconductors and gases on the applied field. This observation is discussed and it is suggested that a form of avalanche breakdown might be the cause of laser-induced damage.
128 citations
TL;DR: In this article, the reflectivity and other optical constants of metals at high temperatures are discussed on the basis of the Drude theory and the theory of electron-phonon collision.
Abstract: The reflectivity and other optical constants of metals at high temperatures are discussed on the basis of the Drude theory and the theory of electron‐phonon collision. The electron‐phonon collision frequency is dependent on the temperature through the temperature dependence of the phonon population. The temperature dependence of the collision frequency determines that of optical properties of metals. Variations of the real and the imaginary parts of the dielectric constant and of the complex refractive index with temperature are considered. General expressions for the temperature coefficients of the optical constants are given. The reflectivity is shown to decrease with increasing temperature. Numerical calculations were carried out for several metals at a few wavelengths and at temperatures from room temperature to their melting temperatures. The results are given in graphs and in a table. Curves for the reflectivity show that the absolute value of the temperature coefficient of the reflectivity is greater for a metal having a lower reflectivity at room temperature. Calculated values of the reflectivity at room temperature are in reasonable agreement with handbook data. However, the calculated reflectivity for silver at its melting point is not coincident with the reported experimental data (the only data available at present), in spite of the qualitative agreement between our results and the experiment. A brief discussion on possible explanations of the discrepancy is made.
TL;DR: In this article, single picosecond light pulses from a mode-locked Nd:glass laser are investigated by several methods, including three-photon fluorescence, photoelectric measurements, and quantitative studies of the contrast ratio of the two-phase fluorescence.
Abstract: Single picosecond light pulses from a mode-locked Nd:glass laser are investigated by several methods. Their temporal structure is studied by two-photon fluorescence. The frequency spectra are measured quantitatively. The energy distribution is simultaneously investigated by three-photon fluorescence, photoelectric measurements, and quantitative studies of the contrast ratio of the two-photon fluorescence. The pulse shape is measured using a method based on the stimulated Raman effect. It is observed that the pulses are weakly asymmetric-the pulse decay is slower (exponential) than the pulse rise (Gaussian). Bandwidth-limited pulses of 4-8 ps are present in the leading part of the pulse train. Substantial frequency broadening develops as the pulse train reaches its maximum and a subpicosecond structure is formed in the trailing part of the pulse train.
TL;DR: In this article, the dependence of spectral narrowing in lasers on the line-broadening mechanism including the effects of saturation and distributed loss has been investigated, and it is found that in the unsaturated regime the narrowing is essentially independent of the resonance broadening mechanism and the narrowed line approaches a Gaussian.
Abstract: The dependence of spectral narrowing in lasers on the line-broadening mechanism is investigated including the effects of saturation and distributed loss. It is found that in the unsaturated regime the narrowing is essentially independent of the resonance broadening mechanism and the narrowed line approaches a Gaussian. The onset of saturation slows or reverses the narrowing process. Experimental results have been obtained using a 3.51-μ xenon laser.
TL;DR: In this article, the authors present experimental and theoretical results for N th harmonic mode locking of a Nd:YAG laser with an intracavity phase modulator operating at N = 2, 3, 4, and 5 times the fundamental c/2L frequency.
Abstract: We present experimental and theoretical results for N th harmonic mode locking of a Nd:YAG laser with an intracavity phase modulator operating at N = 2, 3, 4, and 5 times the fundamental c/2L frequency. The bandwidths of the resulting mode-locked spectra depend upon modulation frequency, modulation depth, and laser cavity losses in good agreement with the Gaussian-pulse analysis of Kuizenga and Siegman [5]. For modulation at N(c/2L) the resulting pulse-repetition frequency is also N(c/2L) in all cases. However, in the N = 2 case, for example, the mode-locked optical spectrum includes every adjacent axial mode component if the laser rod is located near the center of the laser cavity, but only every other axial mode when the rod is located at the end of the laser cavity. This behavior is explained by a Lamb-type theoretical analysis taking into account the competition between the two "hypermodes," or sets of interleaved next-adjacent axial modes, that can oscillate separately or simultaneously in the N = 2 case.
TL;DR: In this paper, a discussion of the roles of various ingredients necessary for optimization of the gas compositions is given and measurements of efficiency, spectral output, small signal gains, and saturation intensity at various temperatures are reported.
Abstract: Some characteristics of CO laser operation are reported. A discussion of the roles of the various ingredients necessary for optimization of the gas compositions is given and measurements of efficiency, spectral output, small signal gains, and saturation intensity at various temperatures are reported. Important mechanisms that dominate the kinetics of the molecules and electrons in electrical discharge systems are described briefly. Several experimental observations are presented to support the interpretations and conclusions that have been drawn regarding the pumping processes and optimum operating characteristics. The possibility of high-power operation of the CO laser with high efficiency is demonstrated by the attainment of laser efficiencies up to 47 percent with small signal gain coefficients of nearly 0.5 percent/cm and a saturation intensity of 15 W/cm2at a gas temperature of 200°K.
TL;DR: In this article, a kind of resonator was found, the radiation of which is insensitive to thermal distortions, and reproducible material processing was achieved in industrial use with a high-precision laser drilling machine.
Abstract: Optical pumping of solid-state lasers induces thermal lensing in the laser crystal. This lansing determines the beam properties in the resonator; the TEM 00 -mode radiation is limited to a small laser rod volume and it depends on the pump power. Especially with pulse-pumped systems, the generation of stable fundamental mode radiation could only be obtained with low efficiency. Laser resonators with optimum TEM 00 mode output were studied considering the thermal lensing. A kind of resonator was found, the radiation of which is insensitive to thermal distortions. The following is determined by parameters g_{1}, g_{2} : \frac{1}{g_{1}}=2g_{2} +^{1} (\frac{a}{b})^{2} + 2\frac{a}{b} , where a and b are distances between rod ends and mirrors, a and b being the distances between the two mirrors and the lens. The predicted beam behavior was verified experimentally with a high repetition rate YAG laser. A high-precision laser drilling machine was constructed with this design. Because of the insensitive properties, reproducible material processing was achieved in industrial use.
TL;DR: In this article, the propagation losses in metal-film-substrate two-dimensional optical waveguides are calculated and the mode-dependent loss can make efficient mode analyzers, useful for integrated optics modulation schemes.
Abstract: The propagation losses in metal-film-substrate two-dimensional optical waveguides are calculated. Losses for confined modes may become large and are at least an order of magnitude larger for TM than for TE modes. Higher order modes suffer more loss than the fundamental mode. Such mode-dependent loss can make efficient mode analyzers, useful for integrated optics modulation schemes.
TL;DR: In this paper, it was shown that a power of 2-4 kW is needed to produce thermally efficient welds in low-thermal-diffusivity plate materials such as 1/2-in stainless steel, and that higher powers are needed for the more highly conducting metals.
Abstract: Experiments performed over the past year have involved the use of near-diffraction-limited lasers at power levels up to 20 kW for welding applications. This is a substantially higher power level than used in all previously reported experiments. As a result of the higher powers, significantly deeper penetration has been achieved. The optical cavity for the lasers used in these tests was an unstable oscillator, producing a near-diffraction-limited output with an obscuration of approximately 50 percent. The measured penetration for these tests is in reasonably good agreement with established correlations for vacuum electron beam welding data, indicating a strong similarity between the two types of welding. It is shown that a power of 2-4 kW is needed to produce thermally efficient welds in low-thermal-diffusivity plate materials such as 1/2-in stainless steel, and that higher powers are needed for the more highly conducting metals.
TL;DR: In this article, a solution of the transition metal complex bis-(4-dimethylaminodithiobenzil)-nickel was used for the Q switching of an Nd-glass laser by a solution in a solution solution of a transition metal.
Abstract: Q switching of an Nd-glass laser by a solution of the transition metal complex bis-(4-dimethylaminodithiobenzil)-nickel is reported The special advantage of the new Q -switch dye lies in its extreme photochemical stability
TL;DR: In this paper, the authors investigated the properties of distributed feedback (DFB) lasers made in active thin-film optical waveguides and obtained narrow-line tunable oscillation.
Abstract: We have investigated some of the properties of distributed-feedback (DFB) lasers made in active thin-film optical waveguides. By optically pumping these guides with spatially modulated light we have obtained narrow-line tunable oscillation. Operation in single-mode waveguides is well behaved and understood. Measurement of the oscillating wavelengths can be used to determine accurately the parameters that characterize the optical waveguide. This DFB measurement technique offers several advantages over the prism-coupler measurement technique for use with active films.
TL;DR: In this article, the operation of a parametric oscillator phase matched in a GaAs thin-film waveguide is considered, and expressions for parametric gain and oscillation threshold are derived.
Abstract: The operation of a parametric oscillator phase matched in a GaAs thin-film waveguide is considered. Parametric equations of motion for interacting waveguide fields at three frequencies are developed. From these equations we derive expressions for parametric gain and oscillation threshold. A specific orientation of GaAs allows optically smooth cleaved surfaces to form the oscillator cavity. Conditions for which three waveguide modes at three different frequencies can be phase matched are presented for several specific waveguide-substrate structures. These conditions are in each case determined for a wide variety of mode orders, for a laser pump wavelength of 1.06 μ, and for a large range of signal wavelengths. The deviation in thin-film thickness that can be tolerated while maintaining phase matching over a given interaction length is calculated. We find that transverse coupling strength and oscillation threshold powers are widely variable for different phase matched mode order combinations. Oscillator frequency tuning is investigated by first deriving expressions for variations in waveguide parameters required to effect tuning over a specific range and then evaluating these expressions for some of the previously determined phase-matching situations.
TL;DR: In this article, a hybrid injection-locking technique was proposed to stabilize a higher power CO 2 ring laser by locking with a stable low-power reference laser, where the higher power laser is tuned to operate on a self-oscillation line different from that of the reference laser.
Abstract: Frequency stabilization of a higher power CO 2 ring laser by locking with a stable low-power reference laser is described. Successful locking is achieved by employing a novel hybrid injection-locking technique. In the hybrid mode, the higher power laser is tuned to operate on a self-oscillation line different from that of the reference laser. Within the frequency-locking range, the self-oscillation of the locked laser is completely quenched, and only the amplified drive power of the locking laser appears. Operation of this hybrid technique relies on the line competition in the homogeneously broadened CO 2 medium. The hybrid technique, which is easily implemented with a simple hill-climbing servo, permits stabilized operation over a variety of laser lines. An analysis of injection locking that explicity includes the saturation of the homogeneous medium is presented. Expressions are obtained for the gain and the phase relationships within and outside the locking region. To demonstrate the potential of the hybrid injection-locking technique, a 60-W CO 2 laser was locked in frequency to a 0.5-W stable oscillator. The experimental data are in close agreement with theory.
TL;DR: In this article, the production of uniform large-volume laser plasmas with electron-ion densities on the order of 1012/cm3 or larger by means of photoionization is investigated.
Abstract: The production of uniform large-volume laser plasmas with electron-ion densities on the order of 1012/cm3or larger by means of photoionization is investigated. An externally applied electric field heats the electron gas to the optimal temperature for excitation of laser levels. Photoionization by intense UV light may take place in a low partial pressure gas of low ionization potential species dispersed throughout the host laser medium, or the laser medium itself may serve as the photoionized species. Both single-photon ionization and two-photon two-step ionization are shown to be applicable.
TL;DR: In this article, the coupling coefficients between two guided modes that are coupled by ripples in the tube wall are derived based on the model of a slab waveguide, and expressions for the leaky mode losses and scattering losses inevitably introduced by the coupling mechanism are also presented.
Abstract: Hollow dielectric waveguides with gas-filled core and a dielectric tube seem promising as laser structures. The tube fulfills the dual role of a guidance structure for the electromagnetic radiation as well as that of a container for the plasma of the gas laser. Feedback for laser oscillation is achieved by providing coupling between forward- and backward-traveling modes by means of periodic ripples of the inner surface of the hollow dielectric tube. This paper is devoted to the derivation of the coupling coefficients between two guided modes that are coupled by ripples in the tube wall. The calculation is based on the model of a slab waveguide. Expressions for the leaky-mode losses and the scattering losses inevitably introduced by the coupling mechanism are also presented.
TL;DR: In this paper, results obtained with TEA CO 2 lasers in both single-pulse and high-repetition-rate operation are described, with output energy of more than 18 J/1 of excited volume, with overall efficiency of 17 percent without arcing.
Abstract: Results obtained to date with TEA CO 2 lasers in both single-pulse and high-repetition-rate operation are described. The special cathode arrangement for triggered discharge permits output energy of more than 18 J/1 of excited volume, with overall efficiency of 17 percent without arcing. Preliminary results obtained with a gas recirculating loop are 100 pulses/s at a 20-J/pulse level.
TL;DR: In this article, a comparison of threshold and slope efficiency for 2-μm laser action in Ho3+-doped YLF and YAG hosts at room temperature is made.
Abstract: A comparison of threshold and slope efficiency is made for 2-μm laser action in Ho3+-doped YLF and YAG hosts at room temperature. Spectroscopic and laser properties of these materials are also discussed.
TL;DR: In this article, the authors extended the steady-state plane-wave theory for the singly resonant parametric oscillator to the case of arbitrary mirror reflectivities using the exact solutions given by Armstrong et al. [3] for the parametric interaction of three traveling waves.
Abstract: Previous steady-state plane-wave theory for the singly resonant parametric oscillator has been extended to the case of arbitrary mirror reflectivities using the exact solutions given by Armstrong et al. [3] for the parametric interaction of three traveling waves. Numerical results are obtained for the efficiency, pump power transmission, optimum output coupling, threshold for the second mode, etc., for parametric oscillators with arbitrary mirror reflectivities and operating under arbitrary power levels. The analysis is also applied to the intracavity-coupled parametric oscillator-upconverter.
TL;DR: In this article, the authors used a simple nozzles to provide flowing thin streams of dye solution having excellent optical quality and stability over substantial areas, used in CW dye lasers instead of confined flows through thin cells, yield reduced lasing thresholds and superior longterm stability.
Abstract: Dyes dissolved in viscous solvents can be pumped through simple nozzles to provide flowing thin streams of dye solution having excellent optical quality and stability over substantial areas. Such free flows, used in CW dye lasers instead of confined flows through thin cells, yield reduced lasing thresholds and superior long-term stability.
TL;DR: In this article, a transversely excited CO 2 laser in a single longitudinal and lowest order transverse mode was used for mode selection in a laser system designed to operate effectively at reduced pressures.
Abstract: High peak-power output has been obtained from a transversely excited CO 2 laser in a single longitudinal and lowest order transverse mode. An intracavity etalon was used for mode selection in a laser system designed to operate effectively at reduced pressures.
TL;DR: In this article, it was found that the 3.51-μ Xenon laser may exhibit relaxation oscillations in the frequency range of 1 to 10 MHz, and the observed features of these fluctuations were in good agreement with theoretical considerations.
Abstract: It is found that under appropriate conditions the high-gain 3.51-μ xenon laser may exhibit relaxation oscillations in the frequency range of 1 to 10 MHz. Experimental investigations have been conducted in both the time and frequency domains. Most of the observed features of these fluctuations are in good agreement with theoretical considerations.