1096results about "Optical wave guidance" patented technology

Tailored doping of barrier layers enables balancing of the radiative recombination among the multiple-quantum-wells in III-Nitride light-emitting diodes. This tailored doping enables more symmetric carrier transport and uniform carrier distribution which help to reduce electron leakage and thus reduce the efficiency droop in high-power III-Nitride LEDs. Mitigation of the efficiency droop in III-Nitride LEDs may enable the pervasive market penetration of solid-state-lighting technologies in high-power lighting and illumination.

The invention discloses a distributed feedback laser and a preparation method thereof, and relates to the field of lasers. The preparation method of the distributed feedback laser comprises the following steps: forming a lower limiting layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper limiting layer, a grating layer, a grating buried layer, a corrosion stop layer, an InP cladding, a barrier gradient layer, a contact layer and a sacrificial layer on a substrate, wherein the sacrificial layer comprises an InP layer and an InGaAs layer which are stacked in sequence; etching to form a ridge waveguide structure; forming an insulating layer; removing the insulating layer in a preset area on the ridge waveguide structure to expose the sacrificial layer; wherein the side wall of the InGaAs layer is completely exposed, and the side wall of the InP layer is partially exposed; and etching to remove the InGaAs layer and the InP layer to form an upper electrode layer and a lower electrode layer. According to the invention, the reliability and the electro-optical conversion efficiency of the distributed feedback laser can be improved.

The invention provides a patterned photonic crystal laser and a preparation method thereof, the laser comprises a substrate, and a first mask layer, a photonic crystal layer and a second mask layer which are sequentially deposited on the substrate, a light emitting area is etched in the central area of the second mask layer, and transparent conductive layers are deposited on the surface of the second mask layer and the light emitting area; a p-annular electrode is arranged on the surface of the transparent conductive layer on the second mask layer, and an n-annular electrode is arranged below the substrate; the photonic crystal layer is composed of a nanorod array and a polymer filled in gaps of nanorods; holes distributed in a patterned array are etched in the surface of the first mask layer, and nanorods are epitaxially grown in hole areas; the nanorod is formed by sequentially depositing a substrate contact layer, a first waveguide layer, a multi-quantum well layer, a second waveguide layer, a coating layer and a component gradient layer. According to the invention, through collaborative design optimization of all the layers, emission of laser with specific wavelength and preparation of a laser emitting laser with single longitudinal mode, narrow linewidth and stable wavelength are realized.

The invention discloses a low-divergence-angle narrow-linewidth high-power semiconductor laser. Relates to the technical field of semiconductor lasers, in particular to a low-divergence-angle narrow-linewidth high-power semiconductor laser. According to the invention, the parabolic waveguide structure is etched in the light field expansion area, and the metal reflector is introduced to realize a novel light field expansion and metal reflector integrated structure, and the transverse divergence angle of a laser mode is reduced through the expansion structure at the tail end of the waveguide. The laser comprises a laser gain area, a light field expansion area and a spectrum purification area at the tail of the light field expansion area. The laser gain region, the light field expansion region and the spectrum purification region at the tail part of the light field expansion region are made of the same laser epitaxial material in the longitudinal direction, the laser gain region is adjacent to the light field expansion region along the horizontal light emitting direction, and the light field expansion region is adjacent to the spectrum purification region at the tail part of the light field expansion region along the horizontal light emitting direction; the longitudinal direction is the direction from the substrate to the contact layer.

A method of fabricating an optoelectronic component, performed on a multi-layered wafer disposed on a substrate. The method comprises the steps of: etching the multi-layered wafer, thereby defining a slab and a multi-layered ridge, the slab having an upper surface below the ridge and being located between the multi-layered ridge and the substrate; selectively epitaxially growing a III-V semiconductor cladding adjacent to a first and second sidewall of the ridge, the cladding layer extending from the upper surface of the slab along the first and second sidewalls, and thereby cladding an optically active waveguide within the multi-layered ridge; and providing a first and second electrical contact, which electrically connect to a layer of the multi-layered ridge and the slab respectively.

High-power, integrated optical amplifiers are described in which gain waveguides of the amplifiers are designed to improve power performance by reducing power saturation effects in the amplifier. The gain waveguides can change, in at least one aspect, along the length of the gain waveguide to reduce gain saturation. Multi-mode optical beams and / or multi-stage amplification can also be employed to reduce gain saturation.

The invention relates to the technical field of semiconductor lasers, in particular to an ultra-narrow linewidth wavelength-adjustable external cavity laser based on a planar metal grating, which comprises a gain chip, and the left end face and the right end face of the gain chip are respectively plated with a high reflection film and a first antireflection film; a planar metal grating waveguide is arranged on the right side of the gain chip, the right end face of the gain chip is aligned and attached to the left end face of the planar metal grating waveguide, and a second antireflection film and a third antireflection film are plated on the left end face and the right end face of the planar metal grating waveguide respectively; the planar metal grating waveguide comprises a grating waveguide substrate, a ridge optical waveguide is arranged on the upper portion of the grating waveguide substrate, an annular resonance optical waveguide is arranged on the front side of the ridge optical waveguide, a planar metal grating is arranged on the upper portion of the ridge optical waveguide, and a top covering layer is arranged on the upper portion of the planar metal grating. Through the centimeter-level metal grating and the low-loss coupling structure, light beam quality with 3dB line width less than 700Hz and M2 less than 0.9 is realized.

The invention provides a semiconductor laser chip and a preparation method, and belongs to the technical field of semiconductor laser chip preparation, and the semiconductor laser chip comprises an N-surface metal, a substrate, an N-type limiting layer, an N-type waveguide layer, a tensile strain quantum well, a P-type waveguide layer, a P-type limiting layer, an ohmic contact layer, a SiO2 insulating layer, a first P-surface metal layer and a second P-surface metal layer which are sequentially arranged from bottom to top. Waveguide grooves are symmetrically formed in the two sides of the ohmic contact layer and penetrate through the ohmic contact layer, the bottoms of the grooves sink to the P-type limiting layer but do not exceed the P-type limiting layer, and a ridge waveguide is formed between the two grooves. The depth of the waveguide groove is of a stepped structure in the longitudinal direction, the depth of the area close to the cavity surface is increased to the N-type waveguide layer, the area completely covers the SiO2 insulating layer and the first layer of P-surface metal, but no second layer of P-surface metal exists, and the longitudinal stepped structure is formed. Through the design of the tensile strain quantum well and the stepped waveguide groove, cavity surface tensile strain release is realized, light absorption is reduced, and the reliability and the service life of the chip are improved.

The utility model relates to the technical field of lasers, and discloses a high-slope-efficiency surface grating surface emitting laser which comprises a substrate, a lower waveguide layer, an active layer and an upper waveguide layer from bottom to top along the cross section. A ridge-shaped waveguide is formed in the middle area of the uppermost layer of the upper waveguide layer, and a Bragg grating is etched on the surface of the ridge-shaped waveguide; the Bragg grating comprises a section of second-order grating located in the middle and two sections of first-order gratings located at the two ends; a lambda / 4 phase shift is arranged in the second-order grating; the lambda / 4 phase shift is located in an etching area or a non-etching area of the first-order grating closest to the second-order grating; when the lambda / 4 phase shift is located in the etching region of the first-order grating closest to the second-order grating, the upward diffraction light power of the second-order grating is maximum, and the downward diffraction light power is minimum; when the lambda / 4 phase shift is located in the non-etching area of the first-order grating closest to the second-order grating, the upward diffraction light power of the second-order grating is minimum, and the downward diffraction light power of the second-order grating is maximum. According to the invention, high-slope efficiency lasing can be realized.

The invention discloses a high-reliability DFB laser and a preparation method thereof, and relates to the field of lasers. The DFB laser comprises a substrate, a bottom electrode, a first epitaxial layer, a second epitaxial layer, a passivation layer, a top electrode and a dielectric film. The second epitaxial layer comprises a body part and at least one ridge waveguide structure, and an isolation groove for exposing the first epitaxial layer is arranged between the body part and the ridge waveguide structure; the passivation layer covers the surface of the body part, the surface and the side wall of the ridge waveguide structure and the side wall and the bottom wall of the isolation groove; the top electrode covers the ridge waveguide structure and the side wall and the bottom wall of the isolation groove, and at least partially extends to the surface of the body part; the dielectric film covers the ridge waveguide structure; the top surface of the dielectric film is higher than the top surface of the top electrode, and the hardness of the dielectric film is greater than that of the top electrode. According to the invention, the yield of the DFB laser can be improved, and the reliability of the DFB laser can be improved.

A continuous-wave perovskite polariton laser device, including an optical microcavity, a spacer layer, and a gain medium. The gain medium is a perovskite material or a composite material containing perovskite, in a form of thin film, microcrystal, phosphor, nanocrystal, quantum dot, or single crystal. The perovskite gain medium is prepared by solution process or vacuum deposition technique, and is combined with an optical resonator. By exploiting the strong interaction between excitons and photons, a steady-state exciton-polariton condensation is formed, enabling the generation of continuous-wave polariton laser emission with a low threshold. The laser device can achieve low-threshold continuous-wave or pulsed lasing emission at room temperature under various light sources pumping or electrical excitation. Its threshold is 1 to 3 orders of magnitude lower than that of conventional semiconductor lasers, with an optimized threshold as low as 0.1 to 1 W / cm2, representing a novel ultralow-power coherent light source technology.

The invention relates to the technical field of semiconductor lasers, in particular to an external cavity laser for realizing narrow linewidth through phase difference regulation and control of a bimetallic Bragg grating, which comprises a gain chip, a first high-reflection (HR) film is plated on the left end surface of the gain chip, and a first anti-reflection (AR) film is plated on the right end surface of the gain chip; a metal Bragg grating waveguide is arranged on the right side of the gain chip, an annular resonance optical waveguide is arranged on the front side of the ridge optical waveguide, the right end face of the gain chip and the left end face of the metal Bragg grating waveguide are aligned and attached to form an outer cavity structure, and the left end face of the metal Bragg grating waveguide is plated with a second anti-reflection AR film. The right end face of the metal Bragg grating waveguide is plated with a third anti-reflection AR film. Tests show that the side mode rejection ratio (SMSR) is increased to 65dB and the line width is compressed to 0.6 kHz by using an interference enhancement effect and a mode suppression mechanism.

The invention provides a buried heterojunction structure, a preparation method thereof and a laser. The preparation method comprises the following steps: primary epitaxy: growing an N-type InP buffer layer, a multi-layer quantum well structure and a P-type InP protective layer on an N-type InP substrate by using an MOCVD (Metal Organic Chemical Vapor Deposition) technology; growing an etching stop layer on the P-type InP protection layer, wherein the etching stop layer is made of an III-V group material; depositing an insulating medium as a mask on the etching stop layer, and etching the etching stop layer and the basic structure layer in a dry or wet etching mode to form a mesa structure; removing the mask on the mesa structure by wet etching; secondary epitaxy: growing a current limiting layer on the mesa structure by adopting an MOCVD (Metal Organic Chemical Vapor Deposition) technology, wherein the current limiting layer covers the whole mesa structure; and forming a funnel-shaped opening on the current limiting layer by wet etching to expose the etching stop layer. According to the invention, the difficulty of growing the current limiting layer by using the MOCVD technology is greatly reduced; the problem of current leakage is effectively suppressed; the current injection efficiency is improved; and the method has good process repeatability and controllability.

The invention discloses a preparation method and structure of a photon integrated laser, and the method comprises the steps: dividing a device into seven functional regions, including two modulator regions, two gain regions, two front grating regions and a common rear grating region; an active material of a modulator region and a passive material of a grating region are respectively formed through two times of butt-joint growth; after sampling gratings are manufactured in the front grating area and the rear grating area, a cladding layer, a contact layer and a ridge waveguide structure grow, cantilever beam heat insulation structures are formed on the two sides of the ridge waveguide of the shared grating area, and finally electrodes of the rear functional areas are manufactured. Wavelength tuning of the two lasers is achieved by sharing the rear grating area, and the size of the lasers is effectively reduced; the cantilever beam structure of the rear grating area is utilized to effectively reduce heat conduction, improve wavelength tuning efficiency and reduce power consumption; through the double-end integrated electro-absorption modulator, bidirectional light emission of a single integrated chip is realized, signal modulation of different bidirectional light emission wavelengths can be carried out, and the utilization rate of optical fiber transmission is improved.

A semiconductor laser (1) comprising a semiconductor body (2) with an active region (20) for generating radiation (8) and an optical interaction structure (3) with structural elements (30) is specified, wherein at least some of the structural elements (30) are arranged at different nominal center distances (35) to each other such that, during operation of the semiconductor laser (1) at a given operating point, local temperature differences in the optical interaction structure (3) reduce differences between the optical path lengths (39) that are assigned to the nominal center distances (35) of these structural elements (30). Furthermore, a method for manufacturing a semiconductor laser (1) is described.

The invention discloses a wavelength thermal tuning photon integrated device and a preparation method thereof.The device comprises a substrate, a modulator layer, a front sampling grating layer, a gain layer, a rear sampling grating layer, a cover layer and an electric contact layer, the cover layer and the electric contact layer jointly form a shallow ridge waveguide structure, and the shallow ridge waveguide structure is transversely arranged in the center of the upper portion of each functional layer; the whole cover layer and the electric contact layer are etched according to a preset ridge-shaped strip pattern, a cantilever beam structure is transversely arranged in the post-sampling grating layer, the cantilever beam structure comprises a cantilever beam and air grooves in the two sides of the cantilever beam, and the cantilever beam is located under the shallow ridge waveguide structure; the cantilever beam structure is formed by etching the rear sampling grating layer below the shallow ridge waveguide structure according to a preset cantilever strip pattern; according to the technical scheme, wavelength thermal tuning is achieved through collaborative design of the shallow ridge waveguide structure and the cantilever beam grating structure, limitation of material carrier concentration is avoided, thermal response is fast, and power consumption is remarkably reduced.

According to the deep ultraviolet laser epitaxial structure and the epitaxial growth method thereof provided by the invention, the Al component of the first waveguide layer is linearly and progressively increased from the side close to the electron injection layer to the side close to the quantum well active layer; or the Al component of the second waveguide layer is linearly and progressively decreased from the side close to the quantum well active layer to the side close to the hole injection layer to form refractive index distribution which takes the barrier layer of the quantum well active layer as the highest refractive index point and gradually decreases towards one side (the n-type side or the p-type side), so that the light field is firmly bound near the quantum well active layer, and the light limiting capability is remarkably enhanced; meanwhile, high-low Al components of the p-type side (the second waveguide layer) gradually change to generate a strong polarization electric field, ionization of a p-type doped acceptor (such as Mg) can be promoted, two-dimensional hole gas (2DHG) can be induced, and the hole concentration is improved; the low-high Al components of the n-type side (the first waveguide layer) are gradually changed, so that two-dimensional electron gas can be induced, and the electron concentration is improved.

The invention discloses a preparation method and structure of a tunable laser, and the method comprises the steps: carrying out the surface layout of a substrate, and sequentially dividing the substrate into a front gain region, a front phase region, a common grating region, a rear phase region and a rear gain region; growing an active layer, manufacturing a butt-joint mask pattern in the gain region, etching to remove the active layer in the common grating region and the phase region, performing butt-joint growth of a passive layer, removing a mask, manufacturing a grating in the common grating region, and growing a cladding and an electric contact layer; manufacturing an inverted table shallow ridge waveguide structure, and etching an electrical isolation trench; and a cantilever arm structure is manufactured and formed in the common grating area, a titanium-platinum heating resistor, a grating electrode and a grounding electrode are manufactured, and the tunable laser is obtained after preparation of a P-surface electrode and an N-surface electrode is completed. The back-to-back double lasers share the thermal tuning grating, double-end light emitting and wavelength synchronous control are achieved, the cantilever arm structure of the grating ridge waveguide is manufactured, energy consumption of wavelength tuning is reduced, and a solution is provided for large-scale use of tunable light emitting chips in the future.

The invention discloses a preparation method and a structure of a novel electro-absorption modulated laser, and the method comprises the steps: symmetrically dividing a substrate into a double-end modulation region, a gain region, a grating region and a phase region, manufacturing a first mask pattern on the surface of the gain region, growing an active layer containing a quantum well structure in a mask gap through a selective region epitaxy technology, forbidden band red shift of the gain region is realized; manufacturing a mask covering the gain region and the modulation region, and etching a non-functional region to expose the substrate; a passive material with a wider band gap is grown in the exposed substrate area in a butt joint mode, and a photon limiting structure is formed; manufacturing a sampling grating through electron beam direct writing, growing a cladding layer and a contact layer, and etching an inverted table shallow ridge waveguide; and finally, etching an electrical isolation trench and manufacturing a double-sided electrode to complete device integration. Through the selective area epitaxial growth technology, active materials with two forbidden bandwidths of the gain area and the modulation area are achieved through one-time epitaxial growth, and a solution with extremely low cost is provided for the wavelength tunable electro-absorption modulated laser.

The invention provides a wide-ridge single-mode semiconductor laser and a manufacturing method thereof.The laser comprises an N electrode, a substrate layer, an epitaxial structure and a P electrode which are stacked in sequence, a grating layer is arranged in the epitaxial structure, and a grating is etched in the portion, close to the center, of the grating layer; the epitaxial structure is partially etched with the area where the grating is located as the center, a ridge-shaped structure is obtained, and the width of the ridge-shaped structure is larger than that of the grating. The grating is arranged in the epitaxial structure, and the high-order mode lasing of the wide-ridge semiconductor laser can be inhibited by regulating and controlling the feedback effect of the grating on different modes of the semiconductor laser, so that the quality of a fundamental mode beam is improved.

The invention provides a micro-disk structure semiconductor laser and a preparation method, and belongs to the technical field of semiconductor lasers. The high-concentration Zn-doped p-GaAs multi-quantum-well multi-quantum-well light-emitting diode comprises a SiO2 barrier layer, an n-GaAs substrate with the thickness of 100 microns, an n-GaAs contact layer with the thickness of 100 nm, a Si-doped n-AlGaInP limiting layer with the thickness of 200 nm, an n-AlGaInP waveguide layer with the thickness of 400 nm, a first GaInP / AlGaInP multi-quantum-well layer, a GaAs barrier layer, a second GaInP / AlGaInP multi-quantum-well layer, an undoped p-AlGaAs waveguide layer with the thickness of 150 nm, a Zn-doped p-AlGaInP limiting layer with the thickness of 200 nm and a high-concentration Zn-doped p-GaAs contact layer with the thickness of 100 nm. By controlling the thickness and the doping concentration of each layer, efficient limitation and injection of carriers are realized; due to the design of the double multi-quantum well layer and the barrier layer, the device can realize stable lasing in two wavebands of 808nm and 650nm; the undoped waveguide layer effectively reduces the optical loss, prolongs the photon lifetime, and improves the laser output efficiency. And the quantum efficiency and the temperature stability of the device are improved.

The invention provides a semiconductor laser element with a spin polarization sub-layer. The semiconductor laser element comprises a substrate, a lower limiting layer, a lower waveguide layer, an active layer, an upper waveguide layer and an upper limiting layer which are sequentially arranged from bottom to top. According to the semiconductor laser element, the spin polarization sub-layers of a multi-layer structure are arranged between the upper limiting layer and the upper waveguide layer in the semiconductor laser element, and the electron mobility distribution characteristic and the piezoelectric polarization coefficient distribution characteristic of each spin polarization sub-layer are limited. Specific electron mobility distribution and piezoelectric polarization coefficient distribution of the spin polarization sub-layer form an asymmetric discrete potential barrier, lattice distortion structure polarization is modulated, charge dipole momentum net accumulation is increased, the piezoelectric polarization effect of the active layer is regulated and controlled, the quantum restriction effect is suppressed, energy band inclination of the active layer is reduced, and hole injection band order is reduced. The overlapping probability of the electron hole wave function is improved, and the internal quantum efficiency is improved.

The invention provides a semiconductor laser and a preparation method thereof. The preparation method comprises the following steps: forming a lower limiting layer on one side of a semiconductor substrate layer along a first direction; a ridge-shaped structure is formed on the side, away from the semiconductor substrate layer, of a part of the lower limiting layer, the ridge-shaped structure comprises a lower waveguide layer, an active layer, an upper waveguide layer, a grating layer and a cover layer which are sequentially stacked in the first direction, and the cover layer is located on the side, away from the upper waveguide layer, of the grating layer; an insulating epitaxial layer is formed on the side, away from the semiconductor substrate layer, of the lower limiting layer, the insulating epitaxial layer is located on the side, away from the semiconductor substrate layer, of the ridge-shaped structure and on the two sides, in the slow axis direction, of the ridge-shaped structure, and the thermal conductivity of the insulating epitaxial layer is larger than that of the active layer; an opening is formed in the insulating epitaxial layer, the opening exposes the cover layer, and the size of the opening in the slow axis direction is larger than that of the ridge-shaped structure in the slow axis direction; an upper confinement layer is formed in the opening.

An optoelectronic device (10) comprises a laser light-emitting component (100) and an optical component (200) with an optical waveguide (201). The laser light-emitting component (100) has a light-exit surface (120) for emitting the laser light and at least one first alignment structure (130) on a first end face (110). The optical component (200) has a light-entry surface (220) on a second end face (210) where the laser light can be coupled into the optical waveguide (201), and at least one second alignment structure (230).The first and second alignment structures (130, 230) are designed to be complementary to each other in order to align the laser light emitting component (100) to the optical component (200) in such a way that the light exit surface (120) and the light entry surface (220) are opposite each other, whereby the laser light is coupled into the optical waveguide (201) in the case of emission of laser light by the laser light emitting component (100).

A light-emitting element array includes a substrate, plural light-emitting elements arranged on the substrate, plural constriction grooves being provided in a periphery of each of the plural light-emitting elements, and forming a current constriction layer that constricts a current flowing through a light-emitting layer by oxidizing the light-emitting layer, and a block separation portion that is formed so as to overlap a part of the plural constriction grooves in plan view, and separates the plural light-emitting elements into plural blocks.

Systems and methods are provided for refractive index engineering for brightness enhancement and kink suppression in optical emitter devices. An example optical emitter device may include a first region that includes a first semiconductor material, an active region located on the first region, with the active region including a pumped active region between a front end and a back end of the optical emitter device, and a plurality of loss structures arranged along at least a portion of at least one side of the pumped active region. The plurality of loss structures may be arranged between the front end and the back end of the optical emitter device. The plurality of loss structures may include two or more continuous etched lines. The plurality of loss structures may include two or more discontinuous etched features.

The invention provides a nitride semiconductor laser. The laser comprises a substrate, a lower coating layer, a lower waveguide layer, an active layer, an upper waveguide layer, an electron blocking layer and an upper coating layer which are sequentially arranged from bottom to top. And the lower waveguide layer comprises any one or a combination of more of InGaN, GaN, InN, AlInGaN, an InGaN / GaN superlattice, an InGaN / AlGaN superlattice, an InGaN / AlGaN superlattice, an InGaN / AlInN superlattice and an InGaN / AlInGaN superlattice. The peak rate electric field distribution of the lower waveguide layer has an arc distribution, and the peak rate electric field distribution has a curve distribution of a function y = logax (a > 1). The drift rate distribution of the saturated electrons of the lower waveguide layer has an arc-shaped distribution, and the drift rate distribution of the saturated electrons has a curve distribution of a third quadrant of a function y = x-b (b > 1, b is an odd number). The density distribution of valence band effective states of the lower waveguide layer has a curve distribution of a third quadrant of a function y = (cx + 1) / (cx-1) (c > 1).

[Task] A semiconductor laser element with reduced light loss is provided. [Solution] A semiconductor laser element emits ultraviolet light and includes an n-side cladding layer, an n-side guide layer, an active layer, a p-side guide layer, and a p-side cladding layer, each made of a nitride semiconductor, in this order upwards. The semiconductor laser element includes a first surface and a ridge portion protruding upwards from the first surface. The first surface is located at the top with respect to a lower end of the p-side guide layer and at the bottom with respect to an upper end of the p-side guide layer. A thickness of the n-side guide layer is thinner than a thickness of the n-side cladding layer. An Al composition ratio of the n-side guide layer is smaller than an Al composition ratio of the n-side cladding layer.a thickness of the p-side guide layer is thinner than a thickness of the p-side cladding layer and thinner than the thickness of the n-side guide layer, and an Al composition ratio of the p-side guide layer is smaller than an Al composition ratio of the p-side cladding layer.,

The invention relates to a semiconductor laser arrangement with a laser-active material comprising layers of different semiconductor materials. A first and a second reflective element are arranged between the laser-active material, the second element being configured for extracting laser light from the laser-active material. According to the invention, at least one of the first and second elements has a layer stack with an electro-optic layer sequence. The electro-optic layer sequence comprises a first conductive and, in particular, transparent layer with a terminal; a second conductive and, in particular, transparent layer with a terminal; and an intermediate, in particular, insulating layer in which an optical parameter can be varied depending on a voltage between the first and the second layer.