JPS62178219A - Optical wavelength selecting element - Google Patents

Abstract

PURPOSE:To select and output an optical signal different in wavelength by forming a liquid crystal layer between dielectric multilayer film filters and changing the optical length and resonance wavelength of the liquid crystal layer on the basis of voltage applied from the external. CONSTITUTION:The dielectric multilayer film filter 2, a transparent electrode 3 and an orientation processing agent 4 are laminated on each melted quartz glass base 1 and the liquid crystal layer 5 is formed between both the bases. When voltage is applied form a power supply 6 to the electrodes 3, the refractive index of the layer 5 is changed in accordance with the applied voltage and the optical length and the resonance characteristics are also changed. An optical signal with wavelength lambdai corresponding to the applied voltage can be selected and outputted by making optical signals with respective wavelengths lambda1-lambdan incident, changing the optical length of the layer 5 inserted between the filters 2 on the basis of the voltage applied from outside and changing the resonance wavelength. Consequently, flexibility as a device can be improved and the element capable of being sued for a demultiplexer or a filter can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used as a duplexer or filter for optical communication equipment. In particular, the present invention relates to an optical wavelength selection element that selects and outputs an optical signal of each wavelength from wavelength-multiplexed optical signals.

[Conventional technology]

Optical wavelength selective elements using dielectric multilayer filters have extremely low loss of high and low refractive indexes with optical thicknesses close to quarter wavelength or half wavelength on glass substrates. The wavelength selectivity of a dielectric multilayer filter in which several layers or ten or more layers of dielectric films are alternately laminated is utilized. That is, the refractive index, number of layers, and layer thickness of each layer are set in order to provide desired wavelength selection characteristics.

In addition, there is an optical wavelength selection element using a tunable wavelength semiconductor laser (Reference: Kikushima, Sano, Nagai, Proceedings of the 1985 National Conference of the Institute of Electronics and Communication Engineers, 885, 1985).
spring).

[Problem that the invention seeks to solve]

However, in the configuration of a conventional optical wavelength selection element using such a dielectric multilayer filter, the wavelength selection characteristics are fixed, so there is a drawback that the selected wavelength cannot be changed after the optical wavelength selection element is manufactured. Ta.

Furthermore, optical wavelength selection devices using tunable wavelength semiconductor lasers require extremely delicate temperature control to set the selected wavelength, and therefore are currently operated at the laboratory level.

SUMMARY OF THE INVENTION An object of the present invention is to improve such conventional drawbacks and provide an optical wavelength selection element that can selectively output wavelength-multiplexed optical signals according to an external operation. do.

[Means for Solving the Problems] The present invention includes an optical resonator in which two mirrors with extremely good flatness are held facing each other in parallel, and the mirrors are set from wavelength-multiplexed optical signals. An optical wavelength selection element having a structure for separating and outputting wavelengths is characterized in that the optical resonator includes a liquid crystal layer and includes an electrode for applying an externally applied voltage to the liquid crystal layer.

The mirror constituting the optical resonator is preferably a dielectric multilayer filter.

[For production]

The present invention provides a liquid crystal layer between dielectric multilayer filters, and takes advantage of the fact that the optical path length of this liquid crystal layer changes depending on an externally applied voltage, and its resonant frequency changes. Different optical signals can be selectively output.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the structure of an embodiment of the present invention. 1st
In the figure, reference number 1 is a fused silica glass substrate, reference number 2 is a mirror formed by a dielectric multilayer filter, and reference number 3 is a mirror made of a dielectric multilayer filter.
Reference number 4 is a transparent electrode, reference number 4 is an alignment treatment agent for aligning liquid crystal, and reference number 5 is a liquid crystal layer. Reference number 6 is a power source connected to the transparent electrode 3 and applying an electric field to the liquid crystal layer 5.

It is configured to input optical signals with wavelengths λ1 to λ7 and selectively output optical signals with wavelengths closer to λ.

It should be noted that the step between the image portions sandwiching the liquid crystal layer 5 is arranged to facilitate manufacturing in connection between the transparent electrode 3 and the power source 6.

The alignment direction of the liquid crystal layer 5 is the same on both substrates. By applying a voltage between the transparent electrodes 3, the refractive index of the liquid crystal layer 5 changes according to the applied voltage, and the resonance characteristics change due to the accompanying change in the optical path length.

FIG. 2 is a diagram showing an incident light spectrum. The incident light includes polarized light whose resonant wavelength changes and polarized light whose resonant wavelength does not change, but here, polarized light whose resonant wavelength changes is input.

FIG. 3 is a diagram showing an example of wavelength selection characteristics of the optical wavelength selection element according to the embodiment of the present invention. Note that in this example, nematic liquid crystal was used for the liquid crystal layer.

FIGS. 3(a) and 3(b) show the transmitted light spectra when no voltage is applied to the liquid crystal layer 5 and when no voltage is applied. As the voltage is applied, the spectrum in Fig. 3(a) continuously changes to Fig. 3(a).
The spectrum changes to b). Note that the polarization direction of the incident light was the same as the alignment direction of the liquid crystal layer 5.

FIG. 4 is a characteristic diagram showing the relationship between applied voltage and resonance wavelength.

The horizontal axis is the device voltage (V), and the voltage applied between the transparent electrodes 3 is the voltage divided by this device voltage, which is approximately 3 to 5 (■)
It is. The vertical axis is the resonant wavelength (μm), and four resonant wavelengths are shown. Note that the thickness of the liquid crystal layer 5 is approximately 10 μm.
and the refractive index n is about 1.5 to 1.6 depending on the applied voltage.
is changing.

In this way, the optical path length of the liquid crystal layer 5 inserted between the dielectric multilayer filters 2 is changed by an externally applied voltage,
By changing the resonant wavelength, it is possible to selectively output an optical signal with a wavelength (λ,) corresponding to an externally applied voltage.

[Effects of the Invention] As explained above, the optical wavelength selection element of the present invention changes the resonant wavelength in the liquid crystal layer by inputting a wavelength-multiplexed optical signal and changing the voltage applied to the liquid crystal layer. An optical signal with a corresponding wavelength can be selected and output using a dielectric multilayer filter.

Therefore, flexibility as a device can be increased, and an optical demultiplexer using this can be used in optical signal processing equipment, optical switching equipment, and the like.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention. FIG. 2 is a diagram showing an incident light spectrum. FIG. 3 is a diagram showing an example of wavelength selection characteristics of the optical wavelength selection element according to the embodiment of the present invention. FIG. 4 is a characteristic diagram showing the relationship between applied voltage and resonance wavelength. DESCRIPTION OF SYMBOLS 1... Fused silica glass substrate, 2... Dielectric multilayer film filter, 3... Transparent electrode, 4... Alignment treatment agent, 5...
...Liquid crystal layer, 6...Power supply. Patent Applicant Nippon Telegraph and Telephone Corporation Agent Patent Attorney Nao Ide
) Incident light S'Y7 torque 1.16 1.26 1.36,. )'AfE
ft7頗-2 1.16 1.26 1.36r1 1ktor %lr 7 m”n Thorn! Voltage (V) 4 (21

Claims (2)

[Claims] (1) Optical wavelength selection that includes an optical resonator in which two mirrors with extremely good flatness are held facing each other in parallel, and the mirrors have a structure that separates and outputs a set wavelength from a wavelength-multiplexed optical signal. An optical wavelength selection element comprising: a liquid crystal layer within the optical resonator; and an electrode for applying an externally applied voltage to the liquid crystal layer. (2) The optical wavelength selection element according to claim (1), wherein the mirror constituting the optical resonator is a dielectric multilayer filter.