JP2003188469A - Laser light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser light source capable of realizing spectrum stabilization with a small and simple configuration when introducing light output from a semiconductor laser into an optical waveguide type wavelength conversion element. . SOLUTION: Semiconductor laser 1 and semiconductor laser 1
A fiber grating 2 having one end 2a connected to a light output section thereof, and an optical waveguide type wavelength conversion element 3 for introducing light whose wavelength is locked by the fiber grating 2 and outputting visible light. Conversion element 3
Is formed of a periodically poled LiNbO ₃ crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light source that stabilizes the wavelength of light output from a semiconductor laser and introduces it into an optical waveguide type wavelength conversion element.

[0002]

2. Description of the Related Art Laser light source devices are used in various technical fields, and one example thereof is a photographic processing device. In this photo processor, R, G, B (red, green,
It is equipped with a laser light source device for outputting laser light of each color (blue), and an image is printed and exposed on a photographic light-sensitive material by laser light optically modulated based on image data.

In the laser light source of each color, the red light uses the output light from the semiconductor laser, but for the green light and the blue light, the near infrared light output from the semiconductor laser is introduced into the wavelength conversion element. Then, the light having a desired wavelength is obtained by wavelength conversion. Such a laser is referred to as an SHG (Second Harmonic Generation) laser, and the use of an infrared semiconductor laser has the advantages of long life and high output.

As the above-mentioned wavelength conversion element, a resonator type and an optical waveguide type are known, but the resonator type is difficult to miniaturize and high-speed modulation, and therefore, the optical type such as a photo processing device is difficult. Not suitable for information processing. On the other hand, the optical waveguide type is
Compact and low cost, suitable for optical information processing.

[0005]

On the other hand, the allowable width when the light is introduced by the optical waveguide type wavelength conversion element is a very narrow range of about 1 nm, and the fluctuation of the spectrum output from the semiconductor laser must be suppressed. I won't. This is because the visible light output from the optical waveguide type wavelength conversion element also becomes unstable due to the fluctuation of the spectrum. However, the semiconductor laser has a property that the spectrum easily changes due to the influence of temperature. Further, the spectrum is likely to change due to the influence of the return light from the end face of the optical waveguide type wavelength conversion element. In order to prevent the returning light from the end face, it was necessary to attach an expensive optical isolator and a large external grating.

The present invention has been made in view of the above circumstances, and an object thereof is to stabilize the spectrum when introducing the light output from the semiconductor laser into the optical waveguide type wavelength conversion element, with a compact and simple structure. It is to provide a laser light source that can be realized by.

To solve the above problems, a laser light source according to the present invention comprises a semiconductor laser, a fiber grating having one end connected to a light output portion of the semiconductor laser, and a wavelength lock by the fiber grating. The optical waveguide type wavelength conversion element for introducing the converted light and outputting the visible light is provided.

According to this structure, one end of the fiber grating is connected to the light output section of the semiconductor laser. The fiber grating refers to a core having a periodic refractive index distribution along the axis of the optical fiber. As a result, it is possible to select a wavelength according to the cycle. Therefore, the wavelength-locked light can be introduced into the optical waveguide type wavelength conversion element by the fiber grating. As a result, it is possible to provide a laser light source that can realize spectrum stabilization with a small and simple configuration.

In a preferred embodiment of the present invention, the optical waveguide type wavelength conversion element is a periodically poled LiNbO.
An example is one formed by ₃ crystals (PPLN). PPLN has the advantage of high conversion efficiency and high-power visible light.

Another preferred embodiment of the present invention is one in which the other end of the fiber grating is connected to the light introducing portion of the optical waveguide type wavelength conversion element.

Thus, the returning light from the end face of the optical waveguide type wavelength conversion element can be surely prevented, and the wavelength of the output light of the semiconductor laser can be locked.

As still another preferred embodiment of the present invention,
The light output unit has a first light output unit and a second light output unit, one end of the fiber grating is connected to the second light output unit, and the other end is subjected to total reflection coating. One of them is configured so that the output light from the one-light output section is directly introduced into the optical waveguide type wavelength conversion element.

Light is output from the semiconductor laser from the side (second light output portion) opposite to the original light output direction (first light output portion). Therefore, one end of the fiber grating is connected to the second light output section, and the other end is subjected to total reflection coating. This total reflection coating can prevent the adverse effect of returning light. Also with this configuration, the wavelength of the output light of the semiconductor laser can be locked.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a laser light source according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the laser light source according to the first embodiment.

Such a laser light source is used, for example, in a laser engine of a photo processor. In recent years, a photographic processing apparatus in which image information is converted into digital data and an image is printed and exposed on a photographic light-sensitive material using the digital image data is becoming mainstream. An exposure engine is used to print an image using this image data. There are various types of exposure engines, and one of them is the laser engine described above.

The laser engine is equipped with a laser light source which emits R, G, and B colors in order to form a color image by exposure. A semiconductor laser is used as a laser light source that outputs red light. Also,
An SHG laser is used for green light and blue light. By using SHG, the wavelength of light can be halved, and a green or blue laser light source can be realized in combination with a semiconductor laser that has a long life and can easily achieve high output.

In FIG. 1, the semiconductor laser 1 is preferably in the form of a semiconductor chip and outputs infrared light or near infrared light. The fiber grating 2 can select and reflect a specific wavelength. One end 2a of the fiber grating 2 is connected to the semiconductor laser 1, and the other end 2b is connected to the optical waveguide type wavelength conversion element 3.
The infrared light or near-infrared light L1 output from the semiconductor laser 1 is introduced into the optical waveguide type wavelength conversion element 3 via the fiber grating 2, and the laser light L2 having a half wavelength is output.

This optical waveguide type wavelength conversion element 3 is made of LiN.
The optical waveguide 3a is formed orthogonal to the layer 3b (PPLN) in which the polarization of the ferroelectric crystal exhibiting a second-order nonlinear optical effect such as bO ₃ is periodically inverted. This structure is characterized by high conversion efficiency and high-power visible light output.

The spectrum of the output light of the semiconductor laser 1 fluctuates due to the temperature change and the return light from the end face of the optical waveguide type wavelength conversion element 3. Therefore, the fiber grating 2 is provided to lock the wavelength of the semiconductor laser. The fiber grating 2 has basically the same structure as an optical fiber, and as shown in FIG. 3, it is composed of a core 20 at the center and a clad 21 surrounding the core 20.

However, what is different from an ordinary optical fiber is that the refractive index changes periodically. An example thereof is shown in FIGS. The fiber grating can be generally manufactured by irradiating a silica single mode fiber with excimer laser ultraviolet light.

(A) is an example in which the refractive index changes in a pulse wave shape, (b) is an example in which the refractive index changes in a sine wave shape, and (c) is an example in which the refractive index changes in a sawtooth wave shape. , (D) are examples in which the refractive index changes into a mountain shape.
(A) is preferable because it is the easiest to manufacture. The wavelength of the selected light can be changed by changing the grating period.

When the light output from the semiconductor laser 1 is reflected by the end face of the optical waveguide type wavelength conversion element 3, light having a wavelength different from the oscillation wavelength is reflected, which becomes a factor of spectrum fluctuation. By using the above fiber grating, it is possible to prevent light having a wavelength different from the oscillation wavelength from returning. That is, wavelength locking of the semiconductor laser can be realized. As a result, the visible light whose output is stable can be output from the optical waveguide type wavelength conversion element 3.

The number of fiber gratings to be connected may be one. The outer diameter is about 5 to 10 μm.
The semiconductor laser may also be in the form of a chip, and the size of its light output portion is about several μm × several μm. Further, for connection, for example, an ultraviolet curable adhesive that allows light to pass therethrough is used.

Next, the structure of the laser light source according to the second embodiment will be described with reference to FIG. The semiconductor laser 1 is the first
It has a light output section 1a (front side) and a second light output section 1b (rear side). The second light output section 1b is an essentially unnecessary part, but light is also output from the rear side. This light causes a spectrum variation. Therefore, the one end portion 4a of the fiber grating 4 is connected to the second light output portion 1b. The other end 4b of the fiber grating 4 is subjected to total reflection coating. The end face of the optical waveguide type wavelength conversion element 3 and the first light output portion 1a of the semiconductor laser 1 are connected as close to each other as possible.

The light L3 output from the second light output section 1b is
The light is reflected by the other end 4b and returns, but only the light of the oscillation wavelength returns, so that the spectrum fluctuation can be suppressed. Further, the semiconductor laser 1 and the optical waveguide type wavelength conversion element 3 are brought as close as possible to each other, and the influence of the returning light from the end face can be suppressed. The near-infrared light L4 output from the semiconductor laser 1 is wavelength-converted to obtain visible light L2 with stable output.

Connection method of fiber grating,
Regarding the internal structure of the fiber grating,
It may be similar to that described in the embodiment.

<Other Embodiments> In this embodiment, the laser light source for the laser engine of the photographic processing apparatus has been described, but the present invention is not limited to this. For example, it can be applied to a color laser printer or a color copying machine.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a laser light source according to a first embodiment.

FIG. 2 is a schematic diagram showing a configuration of a laser light source according to a second embodiment.

FIG. 3 is a diagram showing a structure of a fiber grating.

FIG. 4 is a diagram showing how to change the refractive index of the fiber grating.

[Explanation of symbols]

1 Semiconductor laser 1a 1st optical output section 1b Second optical output section 2,4 Fiber grating 2a One end 2b the other end 3 Optical waveguide type wavelength conversion element

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2K002 AA04 AB12 CA03 DA06 GA04                       HA20                 5F073 AB23 AB25 AB29 BA09 EA03

Claims (4)

[Claims] 1. A semiconductor laser, a fiber grating whose one end is connected to a light output portion of the semiconductor laser, and an optical waveguide type wavelength conversion element which introduces light wavelength-locked by the fiber grating and outputs visible light. A laser light source characterized by having. 2. The laser light source according to claim 1, wherein the optical waveguide type wavelength conversion element is formed of a periodically poled LiNbO ₃ crystal. 3. The laser light source according to claim 1, wherein the other end of the fiber grating is connected to a light introducing part of the optical waveguide type wavelength conversion element. 4. The light output unit has a first light output unit and a second light output unit, one end of the fiber grating is connected to the second light output unit, and the other end is provided with total reflection coating. 3. The laser light source according to claim 1, wherein the laser light source is configured so as to directly introduce the output light from the first light output unit into the optical waveguide type wavelength conversion element.