JPS60205422A - Fabry-perot resonance type polarization plane rotating element - Google Patents

Abstract

PURPOSE:To obtain the small-sized polarization plane rotating element with high performance by controlling a temperature control means on the basis of the output of a transmitted light monitor, and specifying the distance between both reflecting films through the thermal expansion of a magneto-optic medium and increasing magneto-optic effect. CONSTITUTION:Linear polarized light 1 with wavelength lambda which is incident in a (z) direction is reflected several times between reflecting films 3 and 3' provided on both end surfaces of the magneto-optic medium 2' which induces an angle theta0 of Faraday rotation when light passes through the magneto-optic medium 2' in the presence of an impressed external magnetic field 5 while the plane of polarization is rotated, and the light is projected as the sum of respective reflected light electric field vectors. The distance l between the reflecting films is adjusted to an integral multiple of lambda/2 and then the angle theta of Faraday rotation increases the value that the magneto- optic medium 2' has originally. A heater is wound around a resonator so as to the work accuracy of the magneto-optic medium 2' nearly as high as the wavelength of the light, and the thermal expansion due to the temperature rise of the magneto-optic medium 2' is utilized to adjust the distance l between the reflecting films.

Description

DETAILED DESCRIPTION OF THE INVENTION (+1) Technical Field of the Invention The present invention relates to a polarization plane rotating element, and more particularly to a means for significantly increasing the rotation angle of a polarization plane due to the magneto-optic effect based on an optical resonance effect.

(b) Prior art and problems As research into technologies that utilize the magneto-optic effect, such as optical isolators, optical modulators, and magneto-optical memories, has been actively conducted, it has become possible to develop large rotation angles of the plane of polarization using the 7Araday effect. It is becoming important to develop a high-performance 7-Alade single-turn element that obtains the following.

However, conventionally used materials for magneto-optical media, except for some materials used in the infrared region (e.g. Y, I, O), have a low magneto-optical figure of merit, and therefore have a large rotation of the plane of polarization. In order to obtain the angle, it is necessary to increase the size of the element or to lengthen the optical path length by utilizing multiple reflections, which has the disadvantage of inevitably accompanied by large optical loss.

(C) Object of the Invention In view of the above-mentioned conventional drawbacks, it is an object of the present invention to increase the magneto-optic effect of a magneto-optic medium and provide a small and high-performance polarization plane rotation element.

Cd) Structure and object of the invention According to the present invention, there is provided a magneto-optic medium for rotating the plane of polarization using a 7 Abry-Perot resonator comprising a magneto-optic medium having parallel end faces and reflective films on both end faces, A temperature adjusting means for adjusting the temperature of the magneto-optical medium is provided, a transmitted light monitor is provided for monitoring the transmitted light of the magneto-optical medium, and the temperature adjusting means is controlled by the output of the transmitted light monitor. This is achieved by providing a 7-Abry-Perot resonant polarization plane rotation element, which is characterized in that the distance between both reflective films is set to a desired value by thermal expansion of the magneto-optic medium.

(Examples of 61 inventions Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a principle diagram of a one-turn element using seven Abry-Perot resonances.

In the figure, l indicates linearly polarized light, arrows indicate two coordinate directions, and reflective films 8.
3' is provided, and the linearly polarized light l transmitted through the reflective film 8 and incident on the optical medium 2 undergoes multiple reflections at both the reflective films 3 and 8', and then is emitted as shown in transmitted light 4. When the distance between the rain-reflecting films is an integral multiple of the 1/2 wavelength of the linearly polarized light 1, the amount of transmitted light 4 increases, and this phenomenon is called the 71 Briperot resonance effect.

Next, the optical medium 2 is replaced with a magneto-optic medium 2', and the external magnetic field 5 is
Apply. The electric field vector 8 of linearly polarized light l is assumed to have coordinates X and y axes on a plane perpendicular to the two coordinate directions, and the electric field vector salt is plotted as an arrow on the X axis centered on the 0 point as shown in the left diagram of Figure 1. In the case of having a plane of polarization that changes in the direction, the transmitted electric field vector E of the transmitted light 4 is rotated by an angle θ with respect to the X axis, as shown in the right figure of the 1g1 diagram. This is due to the 7 Alladay effect due to the action of the magnetic field.

That is, in the present invention, since the output light vector of an optical resonator is given by the sum of each light wave vector obtained by multiple reflections of the optical resonator in an optical resonant state, reflective films are provided on both end faces of the magneto-optic medium 2' having parallel end faces. A 7-abripe σ-optical resonator is constructed by using the 7-abripe σ-optical resonator to increase the 7-arade rotational power of the magneto-optic medium 2'.

This means that when light passes through the magneto-optic medium 2' once due to the application of an external magnetic field 5, the magneto-optic medium 2' (length! (i.e., the inter-reflection film pressure 1" direct) induces 7 degrees of one rotation angle, etc. Due to the light absorption coefficient α, refractive index n) and the reflective films 3 and 3' (reflectance r) provided on both end faces, the straight line 114 light 1 incident in two directions as linearly polarized light is The light is atomized onto the reflective film 3 while undergoing rotation of the plane of polarization.

Now, assuming that the field vector E0 of the incident 11゛L line 11.1 light 1 is in the X-axis direction as shown in Figure 1, the transmitted lUL field vector I is ``(I R) Re-'''/”・e-18J (eo
ssθ0−slnOo”)+1) l I's+ 1u
rnθFl 66++776 ゝ()+・・・・・・
・・・・・・・・・・・・・・・(A) Represented by:

A=1/ (1-2Re-'e-"eos2θ
. +R2e-d・-4δ)・・・・・・・・・(B) δ−2πlrL/λ・・・・・・・・・・・・・・・
(C). From this, the Faraday rotation angle θ becomes,
Further, the transmittance τ is E 12 TIEII+”.

Now, assuming that the light absorption rate of the magneto-optic medium 2' is α=O, the distance between the reflective films 3 and 3' i:ii I is an integral multiple of λ/2, that is, δ=mπ (where m is a positive integer a). When the transmittance τ≠1, the Faraday rotation angle θ is (1+R) which is the original value of the magneto-optic medium.
/ (1-R) times. Also, the distance l between the reflective films 3 and 3' is an odd multiple of λ/4, that is, a = (m+ 1/2)
When π, the transmittance τ becomes 2. (Mo side) and the Faraday rotation angle θ becomes twice.

1+R From the above, in the Fabry-Perot-resonant polarization plane rotation element, by adjusting the distance l between the reflective films to an integral multiple of λ/2, the 71 rad one rotation angle θ can be adjusted to the original value of the magneto-optic medium 2'. It can be multiplied by (l+K)/H-1t) times.

However, in terms of processing accuracy of the magneto-optic medium 2', it is difficult to obtain an accuracy comparable to the wavelength of light, so the present invention
A heater is wound around the Avry-Perot resonator, and the distance l between the reflective films is adjusted using thermal expansion due to temperature rise of the magneto-optic medium 2'.

Figure @2 shows a cross-sectional view of essential parts of a 7 Abry-Perot resonant type polarization plane rotation element according to the present invention. In the figure, the same reference numerals are given to the parts corresponding to the first cause, and redundant explanation thereof will be omitted.

In the figure, 58 is a coil for applying an external magnetic field, and 6 is a magneto-optical medium 2' (for example, (IJ(J・Ll'E
-tt-net film, etc.). 7 The distance l between the reflective films of the Abry-Perot resonator is λ/2
When the amount of transmitted light becomes an integer multiple of , the amount of transmitted light reaches its maximum value, so it is sufficient to monitor the amount of transmitted light 4 and control the temperature with heater 6 so as to always maintain the amount of transmitted light at the maximum value.

FIG. 3 shows a block diagram of the control system of FIG. 2.

In the figure, 7 indicates an Abry-Perot resonator, 8 indicates a transmitted light monitor, and 9 indicates a temperature regulator that controls the heater temperature so that the amount of monitored transmitted light is maximized.

(f) Effects of the Invention As explained in detail above, according to the 7 Afri-Perot resonant type polarization plane rotating element of the present invention, the magneto-optical medium has 7
It is possible to provide a small-sized, high-performance polarization plane rotation element that can significantly increase the rotation angle by 1 more than the original value.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of a 7-Alade one-rotation element that utilizes 7-Avry-Perot resonance, Fig. 2 is a sectional view of a main part of a 7-Avry-Perot resonance type polarization plane rotation element according to the present invention, and Fig. 8 is a control system of the element. The block diagram is shown below. In the figure, 1 is linearly polarized light and 2' is a magneto-optic medium. 8 and 3' are reflective films, 4 is transmitted light, and 5 is an external magnetic field. 5a is a coil, 6 is a heater, 7 is a Fabry-Perot resonator, 8 is a transmitted light monitor, 9 is a temperature regulator, and θ is 7r, which is the rotation angle of one latte. + 1m 2, t12 U 31゛η

Claims (1)

[Claims] A magneto-optic medium for rotating the plane of polarization using a 7-Abry-Perot resonator comprising a magneto-optic medium having parallel end surfaces and reflective films on both end surfaces, the magneto-optic medium having a temperature adjustment means for adjusting the temperature of the magneto-optic medium. At the same time, a transmitted light monitor is provided to monitor transmitted light of the magneto-optic medium, and the temperature adjustment means is controlled by the output of the transmitted light monitor, so that the distance between the two reflective films is adjusted by thermal expansion of the magneto-optic medium. A 7 Abry-Perot resonant type polarization plane rotation element characterized by having a value of 191 points.