Showing papers by "Kenichi Iga published in 1982"
TL;DR: This paper presents a new development of the distributed-index planar microlens of 2.5-3-mm focal length and 0.15 N.A. and shows that it is usable with optical components in fiber communications and proposes a concept of stacked planar optics consisting of a stack of arrayed planarmicrolenses and other optical components.
Abstract: In this paper we present a new development of the distributed-index planar microlens of 2.5-3-mm focal length and 0.15 N.A. and also show that it is usable with optical components in fiber communications. We then propose a concept of stacked planar optics consisting of a stack of arrayed planar microlenses and other optical components. From this configuration a 2-D array of optical devices is monolithically available, and many discrete components can be separated from the array. An optical tap array has been fabricated as an example of stacked planar optics.
177 citations
TL;DR: By selectively diffusing a dopant into the planar substrate a distributed-index planar microlens has been realized and the focused spot of the collimated He-Ne laser beam was as small as 17 micromphi.
Abstract: Planar technology has been used to make a microlens array monolithically. By selectively diffusing a dopant into the planar substrate a distributed-index planar microlens has been realized. The monomer exchange technique for the plastic substrate and ion exchange and electromigration techniques for the glass substrate are used. In particular a 2-D planar microlens array was fabricated in a glass substrate. Each microlens was 1.2 mm in diameter and the focal length was 9.4 mm. The focused spot of the collimated He-Ne laser beam was as small as 17 micromphi.
93 citations
TL;DR: In this article, a simple stripe laser structure with one etched mirror and one cleaved mirror was proposed, and the threshold currents of devices with 10 μm stripe electrodes were about 180-200 mA.
Abstract: Detailed results on stripe Ga x In 1-x As y P 1-y /InP lasers ( \lambda = 1.3 \mu m) with chemically etched-mirrors are reviewed. These devices are fabricated from GaInAsP/InP wafers grown by liquid phase epitaxy. A simple stripe laser structure with one etched mirror and one cleaved mirror is proposed. Monolithic passivation has been achieved using a Si 3 N 4 film and metal coatings on the etched facets. These processes not only increase the reflectivity of the etched mirrors, resulting in threshold currents even lower than uncoated cleaved devices, but also ease the problem of bonding of the chips on heat sinks. CW operation at room temperature has been achieved. Threshold currents of devices with 10 μm stripe electrodes were about 180-200 mA. Short cavity lasers and integrated monitoring detectors have also been demonstrated.
28 citations
TL;DR: In this article, a surface-emitting GaInAsP/InP injection laser with short cavity length (≅ 10 μm) was made, which operates at 1.22 μm of wavelength with threshold current of 160 mA (33 kA/cm2) at 77 K.
Abstract: We have succeeded in making a surface-emitting GaInAsP/InP injection laser with short cavity length (≅ 10 μm) which operates at 1.22 μm of wavelength with threshold current of 160 mA (33 kA/cm2) at 77 K. No side-emitting mode was observed as a result of preparing long absorbing regions and a small dot electrode (25 μm φ). One of the longitudinal modes, with a spacing of 170 A, dominated above threshold and the far-field radiation angle was sharp (2Δθ = 10°).
27 citations
TL;DR: It is demonstrated that the transverse differential interference method is used as a reliable profiling technique for distributed-index rod lenses, and its accuracy and spatial resolution have been made clear.
Abstract: It is demonstrated that the transverse differential interference method is used as a reliable profiling technique for distributed-index rod lenses, and its accuracy and spatial resolution have been made clear. By the use of this technique the index profile of a distributed-index planar microlens which has 3-D index distribution has been measured.
24 citations
TL;DR: In this paper, a two-dimensional array of planar microlenses was used to monitor a part of light which was transmitted through optical fibres, and the coupling efficiency of the initial device was 52% for coupling multimode graded-index fibres.
Abstract: The letter describes a novel optical tap array by using a two-dimensional array of planar microlenses. The present device is used to monitor a part of light which is transmitted through optical fibres. Planar microlenses to focus the light have been monolithically fabricated by the use of the electromigration technique; the focal length is 3 mm and NA is 0.15. The coupling efficiency of the initial device was 52% for coupling multimode graded-index fibres.
15 citations
TL;DR: Studies on evaluating and measuring aberrations of rod lenses which have mostly parabolic distribution of refractive index have been reviewed and efforts at reducing aberrational errors by controlling the fabrication process are summarized.
Abstract: Studies on evaluating and measuring aberrations of rod lenses which have mostly parabolic distribution of refractive index have been reviewed. Some efforts at reducing aberrations by controlling the fabrication process are also summarized.
10 citations
TL;DR: In this paper, a GaInAsP/InP laser with a current blocking layer made by Be implantation has been fabricated and the minimum threshold current was 160 mA for 2.5 µm width of waveguide and 250 µm cavity length.
Abstract: A GaInAsP/InP laser (λ=1.3 µm) with a current blocking layer made by Be implantation has been fabricated. Be-ions were implanted with 70 keV into an n-InP substrate at room temperature and 2.2×1014 cm-2 of dose. Thermal annealing was applied in a furnace during the LPE (Liquid Phase Epitaxial) growth. The breaking of the forward bias associated with the blocking region was 2 V. The minimum threshold current was 160 mA for 2.5 µm width of waveguide and 250 µm cavity length.
9 citations
TL;DR: In this article, a 3D representation of the refractive index distribution has been proposed, expressed by power series expansion with respect to the transverse and axial distance, where axial symmetry has been assumed.
Abstract: Light rays in a distributed-index planar micro-lens have been traced with the help of a ray equation and the measured value of index distribution, and the light intensity distribution on the focal plane has been obtained. A 3-D representation of the refractive index distribution has been proposed. It has been expressed by power series expansion with respect to the transverse and axial distance, where axial symmetry has been assumed. The obtained ray trajectory and the intensity distribution on the focal plane can be used for the estimation of spot size and spherical aberration. Fairly good agreement has been obtained between the measured intensity distribution and that obtained from ray tracing.
8 citations
TL;DR: Ray-optical treatment in a planar microlens with 3-D distributed refractive index with integral form of the ray equation is presented and its optical properties such as focal length, numerical aperture, and spherical aberration have been estimated.
Abstract: In this paper ray-optical treatment in a planar microlens with 3-D distributed refractive index is presented. An integral form of the ray equation has been derived when the index distribution is expressed by the sum of decomposed functions of radial distance r and axial distance z as in actual fabricated devices. The integral equation is solved independently with respect to r and z, and an analytic form of the ray trace has been obtained in some cases. By applying the result to a planar microlens with index distribution which can be almost approximated by the profile assumed here, its optical properties such as focal length, numerical aperture, and spherical aberration have been estimated.
4 citations
TL;DR: The result shows the applicability of this method of eliminating skew rays to transmit a two-dimensional image through a piece of step-index multimode fiber.
Abstract: We have demonstrated the transmission of two-dimensional images by the use of a single piece of step-index multimode fiber We have used a pair of slits in front of and behind the fiber and those slits were rotated simultaneously to eliminate skew rays In each direction of the slits, light from the associated position of the point source was transmitted through the fiber and the image was reconstructed on film The result shows the applicability of this method of eliminating skew rays to transmit a two-dimensional image through a piece of step-index multimode fiber Some degradations on the image quality might be eliminated by improving the set up or using computer processing
Patent•
31 Mar 1982
TL;DR: In this paper, the precision of an optical demultiplexer and a multiplexer was improved by forming a plane microlens in one body in a plane transparent base material.
Abstract: PURPOSE:To improve the precision of an optical demultiplexer and a multiplexer, by forming a plane microlens in one body in a plane transparent base material so that the plane part of a planoconvex lens part is level with the surface of the transparent base material, and using a laminated body stacked with the microlens through a half-mirror between. CONSTITUTION:An optical fiber 3 for incidence and an optical fiber 4 for projection are connected to one end surface 2a of a laminated body 2 and an optical fiber 5 for projection is connected to the other surface 2b. Light entering a compound lens 9 from the optical fiber 3 strikes a half-mirror 11 through lens parts 7a and 7b to enter the compound microlens 10 through the half-mirror 11 and is guided to the optical fiber 5 for projection through the lens parts 7c and 7d; part of the light is reflected by the half-mirror 11 and transmitted again through the lens parts 7a and 7b to be converged to the end surface of the optical fiber 4 for projection. Thus, the light from the optical fiber 3 is demultiplexed to the optical fibers 4 and 5.
TL;DR: The expression of a distributed index by way of power series expansion is commented on from the viewpoints of wave optics and ray optics and a 3-D expression is proposed.
Abstract: The expression of a distributed index by way of power series expansion is commented on from the viewpoints of wave optics and ray optics. A 3-D expression is also proposed.
TL;DR: The cutoff condition of HE, EH, TE, and TM modes is formulated in an integral equation by using a Sturm-Liouville-type boundary problem as discussed by the authors, and a formula for calculating the cutoff frequencies of the TM01 and HE21 modes is derived in addition to the TE01 cutoff by calculating the eigenvalue of this integral equation.
Abstract: The cutoff condition of HE, EH, TE, and TM modes is formulated in an integral equation by using a Sturm-Liouville-type boundary problem. A formula for calculating the cutoff frequencies of the TM01 and HE21 modes is derived in addition to the TE01 cutoff by calculating the eigenvalue of this integral equation. The cutoff frequencies of the TM01 and HE21 modes are calculated and compared with those of the TE01 mode for various index profiles. As a result, the cutoff frequency of the TM01 mode is dominant for the single-mode limit over frequencies of the TE01, TM01, and HE21 modes for the α-power law index profile. However, in the case of an index profile including a center dip, the cutoff frequency of the TE01 mode dominates the single-mode condition.