RU2456648C1 - Optical switching element based on multilayer dielectric selective mirror - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: layers with large optical thicknesses equal to d_n=x•λ_ref/4 and simultaneously d_n=y•λ_tr/4, where λ_ref is the average wavelength of the reflection band of the optical dielectric mirror, λ_tr is the average wavelength of the transmission band of the optical dielectric mirror, x, y are whole numbers such that x=y±1, are made from ferroelectric material or another optically active material, which provides change in refraction index based on electro-optical, acousto-optical, thermo-optical and mechano-optical effects.

EFFECT: optical switching on at least one output with rate of signal transmission of the nanosecond order, while maintaining accuracy and reliability of the signal.

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Description

The invention relates to integrated optics and can be used to create low-inertia optical logic devices and picosecond switches, devices for processing light information flows that provide switching, branching, spectrum decomposition and filtering of optical signals.

Known non-linear tunable metal-ferroelectric photonic crystal (US Pat. RU 2341817, IPC G02F 1/05, 05/10/2008) and the method of switching it. A photonic crystal contains a substrate, on the surface of which a nonlinear optical film material is applied, on which a diffraction grating made of copper is fixed, while the material allows the light flux to be emitted at a second harmonic frequency, and the diffraction grating is also a system of electrodes for supplying a switching field. Switching the photonic crystal consists in changing the angle of the light beam at the second harmonic frequency. The angle of exit of the light beam from the photonic crystal is changed by doubling the period of the nonlinear diffraction grating due to switching polarization in the ferroelectric film when voltage is applied to the electrode structure in the form of an input diffraction grating. The invention implements switching due to the spatial separation of the optical wavelengths along the exit angle from the tunable metal ferroelectric photonic crystal.

The disadvantage of the device and the switching method is the difficulty of spatial conjugation of the two outputs due to the small difference in the angles of exit from the diffraction grating at a close distance to the diffraction grating; and also in large attenuation due to the divergence of the light beam when entering the waveguide at a distance from the diffraction grating. The disadvantage is the energy inefficiency of the device, since the useful radiation is one of the side lobes from the central maximum.

Closest to the proposed device is an optical switching element (US Pat. RU 2096815, IPC G02B 26/00, 11/20/1997). The optical switching element comprises a substrate and a non-linear element located on the surface of the substrate. The non-linear layer is a thin film of a material with a low refractive index n _n and microcrystals embedded in it, formed from a material with a high refractive index n _in and having a size d determined from the ratio 0.2 · a ₀ <d <3a _o , nm , where a _{0 is the} Bohr radius of the exciton of the initial highly refractive material. The invention implements broadband switching by switching the maximum transmission mode (on) to the dimming mode (off).

The disadvantage of this device is the lack of direct switching between multiple outputs from the device, for switching between different outputs requires an additional device for branching and placing an optical switch in each branch arm.

Known optical multilayer filter is a multilayer dielectric selective mirror (US Pat. RU 2330313, IPC G02B 5/28, 07.27.2008), which consists of N dielectric layers made of materials with different refractive indices, and the optical thickness of each layer is λ / 4 where λ is the average wavelength of the reflection band of the optical filter. In this case, an optical multilayer filter is made up of an input optical transformer, a selective part and an output optical transformer. This device is adopted as a prototype for the claimed device, as it has the most similar structure of the filter element.

A fundamental limitation of the functionality of the device is that the invention provides only passive selection of optical signals at wavelengths.

The objective of the invention is the expansion of the functionality of multilayer dielectric selective mirrors, optical multilayer filters and the creation of an active switching element that provides tunable selective reflection of wavelengths by changing the refractive index based on linear or nonlinear optical, acousto-optical, thermo-optical, electro-optical, mechano-optical effects. The objective of the invention is also to increase the speed of signal transmission and their accuracy and reliability while maintaining a simplified scheme for the formation of conditions for switching in time the directional light flux.

The problem is achieved in that in a tunable multilayer dielectric selective mirror, consisting of an input and output optical transformer, an input polarizer, an external transmission device: electrodes, plates and / or membranes located on the surface of a multilayer dielectric selective mirror, and a selective part containing N dielectric layers made of materials with maximally different refractive indices valid for a given bandwidth friction, such that the optical thickness of any layer - d _n satisfies at the same time: d _n = x · λ _from / 4 and d _n = y · λ _pr / 4, or only d _n = λ _from / 4, where λ _from is the average length wavelengths of the reflection band of the dielectric mirror, λ _pr is the average wavelength of the passband of the dielectric mirror, x, y are integers such that x = y ± 1, layers with large optical thicknesses are made of a ferroelectric material or other optically active material, providing a change in the indicator refraction based on linear or nonlinear optical, acousto-optic , Thermo-optical, electro-optical, mechanooptical or other effects.

In the claimed device, unlike the prototype, switching and separation of optical wavelengths is realized due to a change in the optical length of the structure along the path of the transmitted radiation, which means interference ratios, and a shift in the reflection / transmission range. Radiation is detected directly at the exit from the multilayer structure, without spatial separation of the optical wavelengths by the exit angle from the tunable photonic crystal, without conversion of the frequency of the switched radiation.

The claimed invention differs from US Pat. RU 2330313 the ratio of the thicknesses of the layers and their order, as well as the fact that the active cell in the claimed device is a multilayer dielectric selective mirror is tunable.

The claimed invention differs from US Pat. RU 2096815 in that it implements switching and separation of optical wavelengths in a tunable photonic crystal by changing the optical length of the structure in the path of the transmitted radiation, and therefore interference ratios, and shifting the reflection / transmission range.

The claimed invention is fundamentally different from US Pat. RU 2341817 in that the radiation is detected directly at the exit from the multilayer structure, without spatial separation of the optical wavelengths along the exit angle from the tunable photonic crystal, without converting the frequency of the switched radiation.

These signs are significant and interconnected with the formation of a stable set of essential features sufficient to obtain the desired technical result.

According to the present invention, the claimed objects are characterized by new features, such as:

- a multilayer dielectric selective mirror is made directly on the cleaved optical fiber,

- the functioning of the switching element is carried out by changing the optical length of the photonic crystal,

- switching is carried out using an electric field;

- switching is carried out using a magnetic field;

- switching is carried out using heat exposure;

- switching is carried out by means of acoustic impact;

- has the best form of frequency characteristics by choosing the optimal ratio of the parameters of the photonic crystal.

The present invention is illustrated by specific examples, which, however, are not the only possible, but clearly demonstrate the ability to achieve the above set of features of the desired technical result.

The invention is illustrated in the drawing. The drawing shows a diagram of the device.

Figure 1 shows a schematic illustration of the structure of a tunable multilayer dielectric selective mirror of the form (HL) ⁵ H with optical layer thicknesses d _L = λ _from / 4 = 321 nm, d _H = 7 · λ _from / 4 = 6 · λ _sp / 4 = 2307 nm, refractive indices n _L = 1.48, n _H = 2.3, the abscissa shows the geometric thicknesses of the layers;

figure 2 shows the dependence of the reflection coefficient on the wavelengths of the photonic crystal of figure 1;

figure 3 shows the structure of the optical switch implemented on the electro-optical effect, where 1 is a metal plate, 2 is a multilayer structure, 3 is a polarizer;

figure 4 shows a diagram of the photon crystal of figure 1 in the absence of an electric field;

figure 5 shows a diagram of the photon crystal of figure 1 in the presence of an electric field, shows the ability to control in time the spatial-frequency distribution of the light flux;

FIG. 6 shows the dependences of the reflection coefficient of the photonic crystal under operating conditions with the absence (a) / presence (b) of the electric field on the wavelength, where the graph a is the dependence of the reflection coefficient on the wavelength for the active cell before external exposure and b after exposure .

FIG. 7 shows a photon crystal operation diagram of FIG. 1 in the absence of control intense radiation, where 4 is an optical circulator, 5 is a tunable multilayer dielectric selective mirror, 6 is a multilayer dielectric selective mirror;

in FIG. 8 shows a photon crystal operation diagram of FIG. 1 in the presence of intense control radiation; the possibility of controlling the spatial-frequency distribution of the light flux in time is shown;

The device contains an optically active multilayer cell of the form (HL) ⁵ H with optical layer thicknesses d _L = λ _from / 4 = 321 nm, d _Н = 7 · λ _from / 4 = 6 · λ _pr / 4 = 2307 nm refractive indices n _L = 1.48, n _H = 2.3. The view of the active cell of the switching element is shown in FIG. 1. The longest components of a tunable multilayer dielectric selective mirror (H) are made of optically active material and are capable of changing the refractive index and, therefore, the optical thickness of the component under the action of a control voltage U _control , thereby performing a frequency shift of the reflection coefficient. The offset in the frequency response of a multilayer dielectric selective mirror in the active cell of the switching element is interpreted as wavelength switching. The switching circuit of the active cell of the switching element and the switching along the wavelength before exposure to the control voltage and after exposure are shown in FIG. 4 and FIG. 5, respectively. 6, graph a) shows that the reflection coefficient at a wavelength of 1310 nm is 0.98, which corresponds to a transmit attenuation of 16.99 dB. Figure 6 graph b) shows that the reflection coefficient at a wavelength of 1310 nm is already 0.02, which corresponds to a transmission attenuation of only 0.088 dB.

The active cell of FIG. 1 absorbs optical radiation in very small quantities, as it has a short physical length (7102 nm, the transverse dimension of a single-mode fiber of 10,000 nm) and is made of dielectric, transparent materials. However, there is a phenomenon of divergence of the light flux in the body of an optically active cell and a polarizer, which leads to the main energy losses in the element. There is a problem of introducing a light flux into the ends of the core of the optical fibers, with which the optically active cell and the polarizer are connected. To successfully solve the problem of introducing optical power into the light guide part of the optical fiber with minimal losses at the stage of production of the tunable multilayer dielectric selective mirror, a method for curving the interface of the layers and a method for realizing the design of the tunable multilayer dielectric selective mirror in the fiber body or growing layers directly on one cleaved fiber are used. This is followed by precision docking with the core of the second fiber. Placing the structure in an immersion liquid with a low refractive index, which will perform functions similar to the functions of the sheath of a conventional optical fiber. This is followed by sealing, applying epoxy glue and reinforcing the structure with three steel bars.

In another embodiment of the device, the switching is based on the effect of changing the refractive index of the optically active medium under the influence of intense optical radiation in a tunable multilayer dielectric selective mirror. The switching circuit during the reconstruction of a multilayer dielectric selective mirror under the action of control radiation is shown in FIG. 7. The switching circuit consists of two multilayer dielectric selective mirrors (MDSZ), one of which is tunable (PMDS). Without external influences PMDZZ reflects informative optical radiation at a frequency f _INF , FIG.7. Under the action of intense radiation f _UPR , FIG.8 PMDSZ is tuned to transmit informative optical radiation f _INF . MDSZ is used to reflect the intense control radiation back towards the active cell PMDSZ and prevents the passage of intense non-informative radiation to Output 1. MDSZ is always transparent to informative radiation. It can be seen that, according to Output 1, depending on the control radiation, an informative signal is detected or not detected. If not detected, then it can be detected at Output 2 of the circuit of FIG.7.

In constructive embodiments, in order to expand the functionality of the claimed invention can be made in the form of a volumetric optoelectronic module or a volumetric integrated module, or a circuit board, or a printed circuit board, or a woven board, or a patch board, or a light guide tape, or a flat light guide cable.

This invention can be implemented as a separate device, in the form of integrated optoelectronic modules in fiber-optic telecommunication systems and communication systems, as well as in optical computer systems and computing devices for industrial use.

Claims (1)

An optical switching element consisting of an input and output optical transformer and a selective part based on a multilayer dielectric selective mirror containing N dielectric layers made of materials with the most different refractive indices valid for a given reflection bandwidth, characterized in that at the input to the switching the element has a polarization device, while a device for transmitting external influence is also implemented: electrodes, plates and / or membranes located on the surface of a multilayer dielectric selective mirror, while also the optical thickness of any layer of a multilayer dielectric selective mirror - d _n simultaneously satisfies:
d _n = x • λ _from / 4 and d _n = y • λ _pr / 4, or only d _n = λ _from / 4,
where λ _from is the average wavelength of the reflection band of a multilayer dielectric selective mirror;
λ _CR - the average wavelength of the passband of a multilayer dielectric selective mirror;
x, y are integers such that x = y ± 1,
Moreover, layers with large optical thicknesses are made of a ferroelectric material or other optically active material that provides a change in the refractive index based on linear or nonlinear optical: acousto-optical, thermo-optical, electro-optical, mechano-optical effects.

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