Showing papers in "Optics Letters in 1981"
TL;DR: Multiple diffraction rings appear as a cw laser beam passes through a homeotropic nematic film and are shown to be the result of spatial self-phase modulation due to the laser-induced Freedericksz transition.
Abstract: Multiple diffraction rings appear as a cw laser beam passes through a homeotropic nematic film. The phenomenon is shown to be the result of spatial self-phase modulation that is due to the laser-induced Freedericksz transition.
372 citations
TL;DR: A geometry that allows for the single-mode scanning of lasers that use a diffraction grating as the dispersive element is described and it is observed that under the right conditions a rotation of the tuning element can provide changes simultaneously in cavity length and diffraction angle that exactly match the requirements for continuous single- mode scanning.
Abstract: We describe a geometry that allows for the single-mode scanning of lasers that use a diffraction grating as the dispersive element. It is observed that under the right conditions a rotation of the tuning element can provide changes simultaneously in cavity length and diffraction angle that exactly match the requirements needed for continuous single-mode scanning. As a case study, the method is applied to the grazing-incidence pulsed dye laser.
330 citations
TL;DR: A method for determining the internal structure of a localized scattering potential from field measurements performed outside the scattering volume is developed by using the Rytov approximation.
Abstract: A method for determining the internal structure of a localized scattering potential from field measurements performed outside the scattering volume is developed by using the Rytov approximation. The theory is compared with the inverse-scattering method within the Born and eikonal approximations and found to reduce to these methods in the weak-scattering (Born) and very-short-wavelength (eikonal) limits.
265 citations
TL;DR: Single-mode fiber couplers produced as fused biconical-taper structures are reported on that exhibit low loss, arbitrary branching ratio, polarization independence, and broadband operation in wavelength.
Abstract: Single-mode fiber couplers produced as fused biconical-taper structures are reported on. The devices exhibit low loss (0.5 dB), arbitrary branching ratio, polarization independence, and broadband operation in wavelength.
231 citations
TL;DR: A novel electrodynamic approach is presented that confirms in more detail that the Sagnac phase shift of a ring-waveguide interferometer is the same as for the original Sagnacs experiment with plane waves in a vacuum.
Abstract: We review the kinematic explanation of the Sagnac effect in fiber gyroscopes and recall that the index of the dielectric medium does not have any influence. Furthermore, we present a novel electrodynamic approach that confirms in more detail that the Sagnac phase shift of a ring-waveguide interferometer is the same as for the original Sagnac experiment with plane waves in a vacuum.
220 citations
TL;DR: In this article, deegenerate four-wave mixing experiments have been performed using a liquid suspension of 0.234-μm-diameter latex spheres as the nonlinear medium.
Abstract: Degenerate four-wave mixing experiments have been performed using a liquid suspension of 0.234-μm-diameter latex spheres as the nonlinear medium. The measured effective optical Kerr coefficient, n2, is 3.6 × 10−3 (MW/cm2)−1. This is ~105× the value for CS2. Measured grating reflectivity, formation, and decay times are in reasonable agreement with a simple model assuming Rayleigh scattering and Brownian diffusion.
196 citations
TL;DR: A new all-fiber gyroscope is described, using a laser-diode source to reduce coherent scattering effects and proper choice of modulation frequency to reduce instabilities.
Abstract: A new all-fiber gyroscope is described. All components are constructed directly on a single continuous optical fiber, removing localized sources of reflection. A laser-diode source is used to reduce coherent scattering effects. Proper choice of modulation frequency is shown to reduce instabilities further. Long-term stability at rest of better than 0.2 masculine/h is observed with 30-sec integration time.
188 citations
TL;DR: The problems encountered in the present apparatus, as well as those that are critical in the development of much larger esonators for geophysics and relativity applications, are discussed.
Abstract: As part of a program to develop sensitive laser inertial rotation sensors, we have studied the performance of a passive-resonator technique using a 0.7-m × 0.7-m optical cavity. For an averaging time τ of 10 sec, the random drift was 1.1 × 10−2 deg/h, which was consistent with the shot-noise limit for the present setup. For a longer averaging time the random drift was 5.6 × 10−3 deg/h (τ = 90 sec), showing a slight departure from the shot-noise limit. The problems encountered in the present apparatus, as well as those that are critical in the development of much larger resonators for geophysics and relativity applications, are discussed.
171 citations
TL;DR: An optical fiber gyroscope that, for the first time, is composed completely of single-mode fiber-optic components has increased simplicity and stability over previous bulk-optics designs and has the potential for very high rotation sensitivity.
Abstract: We present an optical fiber gyroscope that, for the first time, is composed completely of single-mode fiber-optic components. This system has increased simplicity and stability over previous bulk-optic designs and has the potential for very high rotation sensitivity.
151 citations
TL;DR: A theory of phase conjugation in asymmetric materials that allow a phase shift between the grating and the light-interference pattern is developed and it is found that when this phase is nonzero, maximum phase-conjugate reflectivity occurs for unequal pump intensities.
Abstract: A theory of phase conjugation in asymmetric materials that allow a phase shift between the grating and the light-interference pattern is developed. We find that when this phase is nonzero, maximum phase-conjugate reflectivity occurs for unequal pump intensities. The conditions for self-oscillation are studied.
150 citations
TL;DR: Fiber-optic sensors are described that utilize the mode-mode interference of the two orthogonal linear polarizations of the HE(11), mode in strongly birefringent single-mode fibers to calculate the sensitivities of various versions of these one-fiber interferometers.
Abstract: Fiber-optic sensors are described that utilize the mode–mode interference of the two orthogonal linear polarizations of the HE11 mode in strongly birefringent single-mode fibers. The sensitivities of various versions of these one-fiber interferometers are calculated. When fibers with high internal stress are used, the temperature sensitivity is reduced by only a factor of 50 compared with that of two-fiber interferometers while the pressure sensitivity is reduced by 7.3 × 103. Thus the cross sensitivity is reduced by a factor of 150.
TL;DR: A general upper limit for this field enhancement is derived on the basis of energy conservation for surface plasmons excited on a metal by an external plane-wave beam through the use of prism or grating couplers or by introducing roughness.
Abstract: Surface plasmons can be excited on a metal by an external plane-wave beam through the use of prism or grating couplers or by introducing roughness. This can enhance the electric field at the surface compared with that in the incident beam, and it has been suggested that this effect is an important aspect of surface-enhanced Raman scattering. A general upper limit for this field enhancement is derived on the basis of energy conservation. Numerical results are given for Ag, Au, and Cu. With a perfect coupler on a Ag surface, the maximum increase of the square of the electric field in the 2–3-eV range is ≅300. On randomly roughened surfaces, the estimated enhancements are of the order of unity.
TL;DR: The related energy transfer and stationary image amplification permit the mode pattern visualization of a vibrating structure in photorefractive BSO crystals to be applied to a real-time optical-processing operation.
Abstract: The energy transfer between two beams (signal and reference, respectively) writing a dynamic-volume hologram in photorefractive BSO crystals is applied to the image amplification of a diffuse object. The image intensity transmitted by the crystal is amplified 10 × in the presence of the pump reference beam. The crystal is used in the drift recording mode (applied electric field, E0 = 10 kV cm−1; fringe spacing, Λ = 3 μm), and beam coupling is induced by the nonlocal response of the crystal that is due to the fringe displacement at a constant speed. We have applied this two-wave mixing configuration to a real-time optical-processing operation; the related energy transfer and stationary image amplification permit the mode pattern visualization of a vibrating structure.
TL;DR: It is shown that the maximum drift rate that is due to faulty polarization control is proportional to the amplitude-extinction ratio for the rejected polarization channel, and in the worst circumstances, the intensity extinction in a typical fiber gyroscope must approach 10(-6).
Abstract: Analysis indicates that strict attention must be paid to polarization control in fiber gyroscopes in order to ensure drift stability. It is shown that the maximum drift rate that is due to faulty polarization control is proportional to the amplitude-extinction ratio for the rejected polarization channel. Consequently, in the worst circumstances, which on present evidence cannot be excluded, the intensity extinction for the rejected polarization channel in a typical fiber gyroscope must approach 10(-6). Options for achieving this control are indicated by the analysis.
TL;DR: A closed-loop, multiturn fiber-optic rotation sensor has been developed that exhibits low noise of the order of 0.1 masculine/h for an averaging time of 30 sec, consistent with the photon-noise limit for this setup.
Abstract: A closed-loop, multiturn fiber-optic rotation sensor has been developed that exhibits low noise of the order of 0.1°/h for an averaging time of 30 sec. This performance is consistent with the photon-noise limit for our setup. The length of the fiber is 200 m, and the coil diameter is 19 cm. Nonreciprocal phase modulation is accomplished with an electro-optic crystal driven at 470 kHz, and closed-loop operation is achieved by means of acousto-optic frequency shifters.
TL;DR: In this paper, phase-matched stimulated four-photon mixing in single-mode fibers in the minimum chromatic dispersion region is described. And phase matching is achieved by using the refractive index slope change and the guiding properties of the fundamental mode.
Abstract: We describe phase-matched stimulated four-photon mixing in single-mode fibers in the minimum-chromatic-dispersion region. Phase matching is achieved by using the refractive-index slope change and the guiding properties of the fundamental mode. Experimental results on large-shift (1600-cm−1) single-idler generation in single-mode fibers with 1.319-μm Nd:YAG laser pumping are presented.
TL;DR: A new technique that utilizes birefringence for phase matching of stimulated parametric emission in a single-mode optical fiber and the frequency shift between the generated frequencies and the pump frequency can be controlled over a wide range by the magnitude of bireFringence built into the fiber.
Abstract: We describe a new technique that utilizes birefringence for phase matching of stimulated parametric emission in a single-mode optical fiber. The frequency shift between the generated frequencies and the pump frequency can be controlled over a wide range (approximately 1000 cm(-1)) by the magnitude of birefringence built into the fiber.
TL;DR: A novel way to enhance the Sagnac effect by using a nonlinear ring interferometer that takes advantage of the nonlinearly induced nonreciprocity of counterpropagating waves caused by the formation of an index grating in the nonlinear medium.
Abstract: We propose a novel way to enhance the Sagnac effect by using a nonlinear ring interferometer. Specifically, we take advantage of the nonlinearly induced nonreciprocity of counterpropagating waves caused by the formation of an index grating in the nonlinear medium.
TL;DR: It was found that ordinary-type Fresnel (zone-plate) lenses and a special-type lens for converting an incident Gaussian intensity distribution into a uniform one have near-diffraction-limited performance.
Abstract: Micro lenses are basic components of micro optics. We have proposed a new fabrication technique for micro lenses that uses electron-beam lithography and have developed an electron-beam lithography system that is specially designed for this purpose. To demonstrate the feasibility of this technique, ordinary-type Fresnel (zone-plate) lenses and a special-type lens for converting an incident Gaussian intensity distribution into a uniform one were designed and fabricated. It was found that these Fresnel (zone-plate) lenses have near-diffraction-limited performance. The fabrication technique and experimental results are discussed.
TL;DR: The conditions on modal amplitudes and modal dispersion necessary for soliton existence are derived in a set of nonlinear coupled equations derived in the frame of coupled-mode theory.
Abstract: Soliton propagation in a multimode optical fiber in the presence of an intensity-dependent refractive index is investigated by means of a set of nonlinear coupled equations derived in the frame of coupled-mode theory. In particular, the conditions on modal amplitudes and modal dispersion necessary for soliton existence are derived.
TL;DR: Results for size parameters that satisfy resonance conditions for various atural modes of oscillation of the cylinder clearly illustrate the physical significance of n and l and show that the internally reflected circumferential waves are localized near, but not confined to, the cylinder surface.
Abstract: Calculations of the electric field distribution within and around an infinite circular dielectric cylinder, having a relative index of refraction of 1.53 and illuminated with plane-wave radiation of wavelength λ, have been performed for size parameters ranging from 39 to 51. Results for size parameters that satisfy resonance conditions for various natural modes of oscillation of the cylinder (mode number n = 53; order numbers l = 1–5) clearly illustrate the physical significance of n and l and show that the internally reflected circumferential waves are localized near, but not confined to, the cylinder surface.
TL;DR: A fiber-optic magnetic-field sensor is constructed by bonding a single-mode fiber to a nickel cylinder by means of the magnetostrictive effect, permitting detection of fields as small as 4.4 x 10(-6) Oe/m of fiber.
Abstract: A fiber-optic magnetic-field sensor is constructed by bonding a single-mode fiber to a nickel cylinder The magnetic field, by means of the magnetostrictive effect, alters the state of polarization of light in the fiber A sensitivity of 176 × 10−2 rad/m Oe is demonstrated, permitting detection of fields as small as 44 × 10−6 Oe/m of fiber
TL;DR: The local parameters of linear, circular, and elliptical birefringence of backscattered light along a single-mode fiber are analyzed, and the twist-bending-induced ellipticalbireferingence in an extremely low bireFringent single- mode fiber is measured using the backscattering method.
Abstract: The local parameters of linear, circular, and elliptical birefringence of backscattered light along a single-mode fiber are analyzed, and the twist–bending-induced elliptical birefringence in an extremely low birefringent single-mode fiber is measured using the backscattering method. The experimental results are in good agreement with the theoretical calculations. For a 130-μm-diameter fiber, twisted by 133°/m and wound around a drum of 15-cm radius, the induced elliptical birefringence is|Ω| = 18°/m at λ = 904 nm.
TL;DR: A major source of noise in fiber-optic Sagnac interferometers was identified to be the fluctuation of the phase of Rayleigh backscattering resulting from minute temperature variations and vibration.
Abstract: A major source of noise in fiber-optic Sagnac interferometers was identified to be the fluctuation of the phase of Rayleigh backscattering resulting from minute temperature variations and vibration. This noise can be reduced either by introducing a phase modulation into the fiber ring or by the use of a low-coherence source. A noise-equivalent rotation rate of 8 x 10(-4) deg/sec was achieved.
TL;DR: Experimentally observed splitting and broadening of the plasma resonance of silver films with adsorbed rhodamine B and nile blue dyes can be described by an effective-medium calculation for the optical response.
Abstract: The optical transmission spectrum of a discontinuous metal-island film is strongly affected by extremely thin layers (<1 monolayer) of dye adsorbate. Experimentally observed splitting and broadening of the plasma resonance of silver films with adsorbed rhodamine B and nile blue dyes can be described by an effective-medium calculation for the optical response: These observations and interpretations have important implications for understanding of surface-enhanced electromagnetic processes.
TL;DR: In this article, the phase-conjugate mirror (PCM) was used to generate a cw dye laser using four-wave mixing in sodium, and the unique bandwidth and pump-probe detuning properties of such a PCM permitted the first reported demonstration of the c/4L spaced paired half-axial modes.
Abstract: We have experimentally demonstrated a cw dye laser incorporating a phase-conjugate mirror (PCM). The mirror was generated by using four-wave mixing in sodium. The unique bandwidth and pump–probe detuning properties of such a PCM permitted the first reported demonstration of the c/4L spaced paired half-axial modes. In addition, the aberration correction ability is demonstrated.
TL;DR: The existence of unguided TM and TE Gaussian beams is derived in a simple way from the wave equation for the vector potential, and the field configurations are discussed.
Abstract: The existence of unguided TM and TE Gaussian beams is derived in a simple way from the wave equation for the vector potential, and the field configurations are discussed. We point out the possibility of a new type of free-electron laser.
TL;DR: It is shown that when little light is lost from the fiber to radiative modes, a constraint of constant total power is introduced that is not present in conventional speckle theory.
Abstract: Modal noise in multimode optical fibers is usually analyzed by using the conventional statistical theory developed for speckle. We show that when little light is lost from the fiber to radiative modes, a constraint of constant total power is introduced that is not present in conventional speckle theory. Experimental results show a marked departure in the behavior of speckle signal-to-noise ratio from the predictions of conventional speckle theory. A suitable modification of this theory is introduced, bringing the theoretical and experimental results into agreement.
TL;DR: By using an evaporated silver film that has a continuously varying thickness, the dependence of surface-enhanced Raman scattering (SERS) on the dielectric properties of the film is demonstrated and support local field models that are based on metal-particle resonances for SERS.
Abstract: By using an evaporated silver film that has a continuously varying thickness, we have demonstrated the dependence of surface-enhanced Raman scattering (SERS) on the dielectric properties of the film. These results support local field models that are based on metal-particle resonances for SERS.
TL;DR: In this paper, the authors demonstrate a fundamentally new type of intrinsic optical bistability that requires no resonant optical cavity and operation is based on mutual self-focusing of counter-propagating laser beams in a nonlinear medium.
Abstract: We experimentally demonstrate a fundamentally new type of intrinsic optical bistability that requires no resonant optical cavity. Operation is based on mutual self-focusing of counterpropagating laser beams in a nonlinear medium.