JPH06175169A - Light frequency converter element - Google Patents

Abstract

PURPOSE:To provide a light frequency converting element capable of sweeping the wavelength of a light frequency converted light in a wide range. CONSTITUTION:An optical waveguide region 14 having a super-high periodic diffraction grating 32 and an optical waveguide region 15 having a super-high periodic diffraction grating 32 whose periodicity is somewhat different from that of the optical waveguide region 14 are formed on one side of an active region 10 composed of a gain region 11 and a supersaturated absorption region 12 and an electrode capable of individually impressing a bias current on each region is formed so as to constitute a light frequency converting element having a DBR laser structure. By performing current injection into an optical waveguide region 15, the wavelength with the highest reflectivity in the diffraction grating waveguide is swept in a wide wavelength range and the converted light wavelength of the light frequency converting element is swept in a wide range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical frequency conversion element made of a semiconductor material having a wide conversion light wavelength sweep width.

[0002]

2. Description of the Related Art Conventionally, as a wavelength conversion element (optical frequency conversion element) capable of sweeping a converted light wavelength, an active region 10 having a saturable absorption region 12 and a gain region 11 as shown in FIG. A structure having a distributed reflection type (DBR type) laser structure in which a diffraction grating type optical waveguide region (DBR region) 13 having the diffraction grating 31 of FIG.
Yamakoshi et al., Postdeadline Papers of OFC'88, P
D-10 (1988)), and as shown in FIG. 3, electrodes 21 and 22 divided into three parts on the upper part of the device and a diffraction grating 31 having a uniform pitch.
And a distributed feedback (DFB type) laser structure in which a current can be independently injected into each part, and the saturable absorption region 12 is formed without applying a current to the electrode 21 (for example, H. Kawaguchi et al., Journal of Quantum E
lectronics, vol. 24, No. 11, pp. 2153-2159, 1988) is known.

[0003]

However, in the optical frequency conversion element having the DBR laser structure shown in FIG. 2, the wavelength sweep of the converted light is performed by the diffraction grating type optical waveguide region 1
The Bragg wavelength was changed in accordance with the change in the refractive index due to the current injection into No. 3, and the wavelength sweep width was only about 3 nm. Further, in the multi-electrode DFB laser structure element shown in FIG. 3, the wavelength of the converted light is swept by changing the ratio of the currents injected into the two gain regions 11, but the wavelength sweep width is about 0.5 nm. Only the value of was realized. Therefore, it is expected to realize an optical frequency conversion element capable of sweeping the wavelength of the optical frequency conversion light in a wider range.

In view of the above problems, an object of the present invention is to provide an optical frequency conversion element capable of sweeping the wavelength of optical frequency conversion light in a wide range.

[0005]

In order to achieve the above object, the present invention provides, in claim 1, an optical frequency conversion element having a saturable absorption region in an active region, a pitch on one optical output side. We propose an optical frequency conversion element that has a distributed reflector in which a diffraction grating with gradually changing is periodically provided.

According to a second aspect, in the optical frequency conversion element according to the first aspect, the distributed Bragg reflector includes at least two or more regions in which the pitches of the diffraction gratings having different pitches are different. We propose an optical frequency conversion device having a structure that has a bias current independently applied to all the regions.

Furthermore, claim 3 proposes an optical frequency conversion element according to claim 2 which has a phase adjustment region.

[0008]

According to claim 1 of the present invention, the distributed reflecting mirror provided on one light output side is periodically provided with a diffraction grating whose pitch is gradually changed, and is diffracted by the diffraction grating. A wavelength having a high reflectance appears periodically, and light having a plurality of wavelengths having a high reflectance is output.

According to the second aspect, the wavelength dependence of the reflectance of the optical waveguide having a region in which the pitch of the diffraction grating is gradually changed (hereinafter, referred to as a super-diffraction grating region) is periodic. A wavelength with high reflectance appears. For example, two super-periodic diffraction grating regions are provided, and the installation periods of the diffraction gratings in the respective super-periodic diffraction grating regions are made different, so that the period in which the wavelength with the high reflectance is periodically appears is slightly reduced. If shifted, current is injected into one of the super-periodic diffraction grating regions, and when the refractive index is changed, the wavelength with the highest reflectance of the diffraction grating region is swept over a wide wavelength range. .

Further, according to claim 3, the phase adjusting region is provided, and when a current is injected into the phase adjusting region, the carrier density is increased and the refractive index is lowered. This allows
The length of the cavity that the light feels can be changed.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, the same components as those in the conventional example described above are represented by the same reference numerals. That is, 11 is a gain region, 12 is a saturable absorption region, and 14 and 15 are optical waveguide regions having a super-periodic diffraction grating 32 in which regions in which the pitch of the diffraction grating is gradually changed are periodically arranged. An optical waveguide region 14 and an optical waveguide region 15 having a super-periodic diffraction grating 32 having a period slightly different from that of the optical waveguide region 14 are formed on one side of the active region 10 composed of the gain region 11 and the saturable absorption region 12. Then, these are integrated to form an optical frequency conversion element having a DBR laser structure. Further, the electrodes 2 are provided in these respective areas 11, 12, 14, 15.
Bias currents can be individually applied by 1, 22, 24, 25, and 27.

The optical frequency conversion operation principle according to the first embodiment having the above-described structure is similar to that of the conventional element, in that the optical absorption loss of the saturable absorption region 12 is reduced by the external injection light to oscillate the element. The optical frequency is converted by immersing yourself in the room. That is, by injecting a bias current into the gain region 11 existing in the active region 10, the gain region 11 has a certain amount of gain, but due to the absorption loss of light in the saturable absorption region 12, the device is lost. Is set not to oscillate. By injecting signal light into the device in this state from the outside and reducing the absorption loss in the saturable absorption region 12, the total loss inside the device becomes balanced with the gain in the active region, and the device starts oscillation. . (For example, H. Kawaguchi et al., Jourana
l of Quantum Electronics, vol. 24.No.11, pp.2153-
(2159, 1988) Further, the operating principle of the converted light wavelength sweep of the optical frequency conversion element according to the present invention is as described below. That is, the state of the pitch change of the super-periodic diffraction grating formed in the optical waveguide regions 14 and 15 is shown in FIG. 4, and the region where the pitch of the diffraction grating continuously changes from Λb to Λa is periodic with the period Λ. Exists in. In the figure, the horizontal axis represents the distance and the vertical axis represents the grating pitch of the diffraction grating.

Here, the wavelength dependence of the reflectance of the optical waveguide regions 14 and 15 provided with the super-periodic diffraction grating structure in which the pitch of the diffraction grating is changed as shown in FIG. 4 is schematically shown in FIG. Like In the figure, the horizontal axis represents the wavelength and the vertical axis represents the reflectance, and (a) of FIG. 5 shows the wavelength dependency of the reflectance of the super-period diffraction grating region of the optical waveguide region 14, for example. (B) of 5 indicates the wavelength dependence of the reflectance of the super-periodic diffraction grating region of the optical waveguide region 15. In this way, the two optical waveguide regions 14 and 15 are slightly shifted in the cycle of wavelengths exhibiting high reflectance. For example, the high reflectance wavelength period in the optical waveguide region 15 is set to 9.5 nm, and the high reflectance wavelength period in the optical waveguide region 14 is 10 nm.
Is set to be slightly different from.

Further, W in the figure indicates the maximum wavelength change range that can be changed when the refractive index is changed by current injection. Here, for example, the current injection is shown in FIG.
The optical waveguide region 15 shown in FIG. First, when no current is injected into the optical waveguide region 15, the wavelength of the reflectance peak on the longest wavelength side matches the reflectance peak wavelength of the optical waveguide region 14, and the reflectance at this wavelength becomes maximum. As a result, the converted light oscillates at this wavelength. Next, by injecting a current into the optical waveguide region 15, the refractive index of the optical waveguide region 15 decreases, and as a result, the reflectance peak wavelength shifts to the short wavelength side while keeping the period substantially constant. Therefore, first, it coincides with the high reflectance peak wavelength existing on the longest wavelength side of the optical waveguide region 15,
The converted light oscillates at this wavelength.

As the amount of current injected into the optical waveguide region 15 is increased, the reflectivity of the optical waveguide region 14 and the optical waveguide region 15 is remarkably wider than the wavelength change amount W caused by the high reflectivity change. It becomes possible to sweep the highest wavelength.

As described above, two or more super-periodic diffraction grating regions are formed in the diffraction grating region of the DBR laser structure optical frequency conversion element, and a current is injected into one of the super-periodic diffraction grating regions to widen the wavelength range. It is possible to sweep the wavelength with the highest reflectance of the diffraction grating waveguide over the entire wavelength range, and it is possible to sweep the converted light wavelength of the optical frequency conversion element in a wide range.

FIG. 6 shows the result when a current is injected into the optical waveguide region 15. In the figure, the horizontal axis represents the injection current and the vertical axis represents the converted light wavelength. In this case, the full-wavelength sweep width of the converted light is 100 with a wavelength jump.
nm value can be obtained, and the wavelength sweep width of the conventional device is 3n
It has become possible to sweep the converted light wavelength in a dramatically wider range than m.

FIG. 7 is a block diagram showing a second embodiment of the optical frequency conversion element according to the present invention. In the figure, the same components as those of the first embodiment described above are designated by the same reference numerals and the description thereof will be omitted. Further, the difference between the first embodiment and the second embodiment is that in the second embodiment, the phase adjustment region 16 is provided between the saturable absorption region 12 and the optical waveguide region 14 of the first embodiment. There is a point. This phase adjustment area 16
Has a function of lowering the refractive index by injecting an electric current to increase the carrier density, thereby changing the length of the cavity that the light feels. By injecting a current into this phase adjustment region 16, the wavelength of the converted light from the optical frequency conversion element shown in the first embodiment can be further finely adjusted, and as shown in FIG. In the example, in the wavelength range where the jump of the converted light wavelength was shown,
It has become possible to slightly sweep the converted light wavelength.

In the first and second embodiments, two optical waveguide regions having a super-periodic diffraction grating are arranged, but the number of optical waveguide regions is not limited to this, and the same effect can be obtained by providing three or more optical waveguide regions. It goes without saying that you can get it.

Further, when only one optical waveguide region having a super-periodic diffraction grating is provided, it can be easily understood that the wavelength of the input signal light can be simultaneously converted into plural kinds of wavelengths and outputted. Let's do it.

[0021]

As described above, according to the first aspect of the present invention, the distributed reflecting mirror provided on one light output side is periodically provided with a diffraction grating whose pitch is gradually changed. Therefore, wavelengths with high reflectance appear periodically, and light with multiple wavelengths with high reflectance is output.Therefore, the wavelength of optical frequency conversion light can be swept in a wide range, and the wavelengths of input light can be changed simultaneously. It can be converted into the wavelength of the seed and output.

According to a second aspect of the present invention, at least two super-periodic diffraction grating regions are formed in which regions in which the pitch of the diffraction grating is gradually changed are periodically arranged, and the periodic structure is formed in each region. Since the structure has a slightly shifted period, when the refractive index is changed by injecting a current into one of the super-periodic diffraction grating regions, the wavelength with the highest reflectance in the diffraction grating region is in the wide wavelength range. Since it is swept over, the wavelength of the converted light from the optical frequency conversion element can be swept over a significantly wider wavelength range than that of the conventional element.

Further, according to claim 3, in addition to the above effect, when the current is injected into the phase adjustment region, the carrier density increases and the refractive index decreases, so that the length of the cavity that the light feels is increased. Since it can be changed, even in the wavelength region where the spread of the converted light wavelength is shown, it is possible to slightly sweep the converted light wavelength, and it is possible to further finely adjust the converted light wavelength, which is a very excellent effect. It is a thing.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an optical frequency conversion element according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional optical frequency conversion device having a DBR laser structure.

FIG. 3 is a configuration diagram showing a conventional optical frequency conversion element having a multi-electrode DFB laser structure.

FIG. 4 is a diagram showing a pitch of a super-periodic diffraction grating.

FIG. 5 is a diagram showing wavelength dependence of reflectance of a super-periodic diffraction grating optical waveguide.

FIG. 6 is a diagram showing a converted light wavelength sweep characteristic of the optical frequency conversion element according to the first embodiment of the present invention.

FIG. 7 is a configuration diagram showing an optical frequency conversion element according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a converted light wavelength sweep characteristic of the optical frequency conversion element according to the second embodiment of the present invention.

[Explanation of symbols]

10 ... Active region, 11 ... Gain region, 12 ... Saturable absorption region, 13 ... Diffraction grating type optical waveguide region (DBR region), 1
4, 15 ... Optical waveguide region, 16 ... Phase adjustment region, 21 ...
Gain region current injection electrode, 22 ... Saturable absorption region current injection electrode, 23 ... DBR region current injection electrode, 24, 25 ... Optical waveguide region current injection electrode, 26 ... Phase adjustment region current injection electrode, 27 ... Board side electrode, 31 ... Diffraction grating, 32 ... Super periodic diffraction grating.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yuzo Yoshikuni 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. An optical frequency conversion device having a saturable absorption region in an active region, which has, on one light output side, a distributed reflector in which a diffraction grating whose pitch is gradually changed is periodically provided. An optical frequency conversion element characterized by the above. 2. The distributed Bragg reflector has at least 2 different installation periods of the diffraction grating with the pitch gradually changed.
The optical frequency conversion element according to claim 1, wherein the optical frequency conversion element has at least one region and has a structure capable of independently applying a bias current to all the regions. 3. The optical frequency conversion element according to claim 2, which has a phase adjustment region.