JPS63131125A - Light-driven optical switching device - Google Patents

Abstract

PURPOSE:To obtain a compact system on the whole by arranging an optical modulating element on the optical path of input light together with a polarizer and an analyzer and driving the optical modulating element with the output of a photoelectromotive force element. CONSTITUTION:When signal light hnu1 is off and the photoelectromotive force element 1 is irradiated with no light, input light hnu2 passes through the polarizer 3, optical modulating element 2, and analyzer 4 as it is and reaches a photodetector 5. Then when the signal light hnu1 is turned on and is incident on the photoelectromotive force element 1, the element 1 generates an abnormally high voltage, which is applied to the element 2. The electromotive force voltage of the element 1 is so adjusted that the applied voltage is as high as the half- wavelength voltage of the element 2, and then the input light hnu2 shifts in phase by 180 deg. in the element 2, so its plane of polarization rotates by 90 deg., so that the light passed through the element 2 is cut off. Consequently, no electric power is required to operate the element 2 and the compact, low-cost switching device is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an optically driven optical switching device using a photovoltaic element, and can be used, for example, in optical communications.

(Prior Art) For example, in the field of optical communications, an optical switching device called an optical shutter is used that turns on and off light according to a signal.

In a conventional optical switching device, a light modulation element is arranged along with a polarizer and an analyzer on the optical path of input light, and a half-wave voltage of the light modulation element is applied to the light modulation element, and this half-wave voltage The light is switched on and off according to the signal. This conventional optical switching device requires a power source to drive the optical modulation element with an input signal, which makes it difficult to downsize the entire system including the optical switching device.

(Purpose) The present invention has been made to solve the above-mentioned conventional problems, and the present invention eliminates the need for a power source to drive the light modulation element by driving the light modulation element with the output of a photovoltaic element. It is an object of the present invention to provide an optically driven optical switching device that allows the entire system to be made more compact.

(Structure) The present invention arranges a light modulation element along with a polarizer and an analyzer on the optical path of input light, and converts the output voltage of the photovoltaic element that generates a voltage by irradiation of signal light to a half wavelength of the light modulation element. The present invention is characterized in that an optical switching signal is obtained through the analyzer by applying a voltage to the optical modulation element.

Hereinafter, embodiments of an optically driven optical switching device according to the present invention will be described with reference to the drawings.

In the figure, a polarizer 3, a light modulator 2, an analyzer 4, and a photodetector 5 are arranged in this order on the optical path of input light. The polarizer 3 and the analyzer 4 are in a parallel Nicol state with each other. The output of the photovoltaic element 1 is applied to the light modulation element 2, and the light modulation element 2 is driven by the output voltage of the photovoltaic element 1. The photovoltaic element 1 is irradiated with driving signal light that is turned on and off according to the signal.

Here, it is assumed that the input light is hv2 and the signal light is hv1. When the signal light hv1 is off and the photovoltaic element 1 is not irradiated with light, the input light hv2 passes through the polarizer 3, the light modulator 2, and the analyzer 4 as it is, and reaches the photodetector 5.

Next, the signal light hν1 is turned on and this turns on the photovoltaic element 1.
When the light is incident on the photovoltaic element 1 , an abnormally high voltage is generated in the photovoltaic element 1 , and this voltage is applied to the light modulation element 2 . If the electromotive force of the photovoltaic element 1 is adjusted so that this applied voltage is equal to the half-wavelength voltage of the light modulation element 2, the phase of the input light hν2 will change by 180° within the light modulation element 2. , the plane of polarization is rotated by 90', and the plane of polarization of the light that has passed through the light modulation element 2 is perpendicular to the plane of polarization of the analyzer 4, so that the light is blocked. In this way, it has an optical switching function, and if the light after switching is detected by the photodetector 5,
A signal corresponding to the signal light hv1 can be obtained.

As is clear from the above explanation, the drive signal of the illustrated optical switching device is light, and this light generates an electromotive force, and by applying this electromotive force to the light modulation element 2, the input light is turned on and off. As a result, a compact and low-cost optical switching device can be provided without requiring a power source to operate the optical modulation element 2.

Here, we will explain about photovoltaic elements. They utilize a phenomenon observed in some materials that exhibit piezoelectricity, and are characterized by the generation of an abnormally large electromotive force when irradiated with light.

This phenomenon is caused by LiNbO3, KNbO3, BaTiO
3. SBN.

It has been observed in many materials such as BNN and PLZT.

Next, a more specific example of the optically driven optical switching device according to the present invention will be described.

PLZT was used as the photovoltaic element, and lateral type LiNbO3 was used as the optical modulation element to reduce half-wave voltage.

PLZT as the photovoltaic element was produced by hot pressing, optically polished on the light incident surface side, and further subjected to poling treatment. 100 mW/c as irradiation light source
As a result of measuring the photoelectromotive voltage by irradiating the PLZT with a mercury lamp of m2, an electromotive voltage of 280V was obtained. The above-mentioned light modulation element made of LiNbO3 was set as a horizontal type with a length-to-thickness ratio so that the above-mentioned electromotive voltage of 280 V became a half-wavelength voltage.

The photovoltaic element and the light modulation element described above were arranged as shown in the figure, a He-Ne laser was used as the light source of the input light, and a mercury lamp was used as the driving signal light.

First, input light is irradiated through the polarizer 3 to the light modulating element 2 between the polarizer 3 and the analyzer 4 which are in a parallel Nicol state, and after passing through the analyzer 4, the light is received by the photodetector 5 and its output is I tried to read it. Next, when driving signal light was irradiated onto the photovoltaic element 1 in this state, the amount observed by the photodetector 5 of the input He-Ne laser light was 1.2 Xl0-' in extinction ratio display. indicates the value,
It was confirmed that input light was completely blocked as a result of irradiation with driving signal light.

I didn't check the response time, but expect extremely fast switching.

In the above specific example, a mercury lamp was used as the light source of the signal light, but if the material of the photovoltaic element is selected appropriately, it is thought that it can also be driven by laser light, and further applications are expected in the future. can.

(Effects) According to the present invention, an electromotive force is generated by light using a photovoltaic element, and input light is turned on and off by applying this electromotive force to a light modulation element. It is possible to provide a compact and low-cost optical switching device that does not require a power source to operate the device.

[Brief explanation of the drawing]

The figure is an optical layout diagram showing an embodiment of an optically driven optical switching device according to the present invention. 1... Photovoltaic element, 2... Light modulation element, 3...
・Polarizer, 4...analyzer.

Claims (1)

[Claims] A light modulation element is placed on the optical path of input light together with a polarizer and an analyzer, and the output voltage of the photovoltaic element that generates a voltage upon irradiation with signal light is applied to the light modulation element as a half-wave voltage of the light modulation element. An optically driven optical switching device which obtains an optical switching signal through the analyzer by applying a voltage.