JP2004063828A - Laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser device which can continuously change (vary) the wavelength of a laser beam for output. <P>SOLUTION: A semiconductor optical amplifying element 1 can generate and amplify light by injecting an electric current into a light reflection plane 11, a light emitting plane 12, and a region sandwiched between these planes. To the light emitting plane 12, an optical fiber 5 having a grating therein is arranged oppositely via an optical element 3 which is transparent and has a positive refractive-index temperature coefficient to the light emitted from the semiconductor optical amplifying element 1. The optical element 3 and the optical fiber 5 are fixed to a base 6, and a Peltier element 7 is arranged on the base 6 to control their temperatures. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention combines a semiconductor optical amplifying element having a function of generating and amplifying light by injecting a current with an optical fiber in which a grating that reflects only light of a predetermined wavelength is formed, and the grating is formed through the optical fiber. More particularly, the present invention relates to a laser device that outputs a laser beam of a predetermined single wavelength determined by the formula (1), and more particularly, to a laser device that has a wavelength variable function and is capable of changing a laser output wavelength.
[0002]
[Prior art]
This type of laser device is, for example, a semiconductor optical amplifier having a light reflecting surface and a light emitting surface and having a function of generating and amplifying light by injecting a current as shown in Japanese Patent No. 3120828. An optical fiber (optical fiber grating) in which a grating that reflects only light of a predetermined wavelength is formed on the light emitting surface side of the semiconductor light emitting element as an element, and a current is injected into the semiconductor light emitting element to thereby form a semiconductor light emitting element. The stimulated emission light generated in the above is repeatedly amplified in a Fabry-Bellows type resonator composed of a light reflecting surface and a grating, and then a predetermined single wavelength laser light determined by the grating is output through an optical fiber. It is configured to be performed.
The patent is directed to effectively prevent the occurrence of kink in the injection current-light output characteristics of laser light. For this purpose, the semiconductor light emitting device is a laser diode chip for the 1.48 μm band, and the grating has The reflection bandwidth is set to 2 to 5 nm, which is larger than the wavelength interval of the longitudinal mode of light resonating on the light reflecting surface and the light emitting surface of the semiconductor light emitting device.
[0003]
Further, it is known that the center wavelength of the reflection peak of an optical fiber having a grating formed (built-in) therein has a temperature dependence that shifts to a longer wavelength side due to a temperature rise. (July 1999, Furukawa Electric Hourly Report, No. 104, pp. 63-68).
Therefore, in a laser device having a semiconductor optical amplifier element and an optical fiber grating disposed on the light emitting surface side of the semiconductor optical amplifier element disclosed in Japanese Patent No. 3120828, a function to vary the wavelength of laser light to be output is required. For example, a configuration is conceivable in which a temperature adjusting function is provided in a grating section of an optical fiber grating to make the temperature variable and make the reflection peak wavelength of the grating variable.
[0004]
[Problems to be solved by the invention]
However, in the configuration in which the temperature of the grating section is varied by providing a temperature control function (mechanism) to vary the reflection peak wavelength of the optical fiber grating, there is the following problem.
That is, in an optical resonator including a semiconductor optical amplifier and a light reflecting surface of the semiconductor optical amplifier and a grating in a laser device having an optical fiber grating disposed on the light emitting surface side thereof, the effective resonator length is L. When the oscillation wavelength is λ, the wavelength interval Δλ is represented by Δλ = λ ² / (2L), so that laser oscillation can be performed only at a fixed wavelength having the wavelength interval Δλ.
Therefore, in this type of laser device, the wavelength of the output laser light (laser oscillation wavelength) can be changed only in discrete steps at intervals of Δλ, and the laser oscillation wavelength (wavelength of the output laser light) is continuously changed. It is impossible to change to.
[0005]
Accordingly, the present invention has been made to solve the above-described problems, and has as its object to provide a laser device capable of continuously changing (variable) the wavelength of output laser light.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, a laser device according to the present invention is a semiconductor device having a function of generating and amplifying light by injecting a current into a light reflecting surface, a light emitting surface, and a region sandwiched between these surfaces. An amplifying element, comprising an optical fiber in which a grating arranged in the direction of the light emitting surface and reflecting only a predetermined wavelength is formed, and generated by a semiconductor optical amplifying element by an optical resonator constituted by the light reflecting surface and the grating. A laser device that emits laser light to the outside of an optical resonator by oscillating light, and is provided between an optical fiber and a semiconductor optical amplifying element, and is transparent and positively refracted with respect to light generated by the semiconductor amplifying element. An optical element having a rate temperature coefficient, and temperature control means for changing and controlling the temperatures of the optical fiber and the optical element are provided.
[0007]
Preferably, the optical fiber and the optical element are held on a single base, or on each base, and the temperature control is to control the temperature of the base. It is preferably a temperature control element such as a Peltier element.
[0008]
According to such an invention, the temperature of the base is changed by the temperature control element to change the temperature of the optical fiber, thereby changing the reflection peak wavelength of the grating, and at the same time, the positive refractive index installed on the base. When the temperature of the optical element having the temperature coefficient is changed, the effective resonator length changes, so that the wavelength of the longitudinal mode changes.
Moreover, since the temperature coefficient of the refractive index of the optical element is positive, for example, when the temperature of the optical fiber rises and the reflection peak wavelength changes to the longer wavelength side, the temperature of the optical element also rises and the optical element As the refractive index of the laser increases, the effective resonator length increases, and the wavelength of the laser also changes to the longer wavelength side, so that the wavelength of the laser can be continuously changed.
[0009]
Further, in the present invention, the semiconductor optical amplifying element operates in a certain wavelength band of 900 nm or more, and the distance between the light reflecting surface of the semiconductor optical amplifying element and the end of the grating closer to the semiconductor optical amplifying device is 20 mm or less. Wherein the grating has a reflection bandwidth of 1.5 nm or less and outputs single-mode laser light.
[0010]
According to such an invention, the wavelength interval of the longitudinal mode of the laser light determined by the oscillation wavelength and the effective resonator length of the optical resonator including the light reflecting surface of the semiconductor optical amplifier and the grating is about 0. .02 nm or more.
In addition, by setting the reflection bandwidth of the grating to 1.5 nm or less, the reflectance at a wavelength separated by 0.02 nm from the reflection peak wavelength of the grating becomes lower than the reflectance at the reflection peak wavelength by 2% or more. Only the longitudinal mode that matches the peak wavelength can be selectively oscillated, and the output laser light can be set to the single mode. Single mode laser light is useful for application to spectroscopic analysis and the like.
[0011]
Further, according to the present invention, the semiconductor optical amplifying element operates in a certain wavelength band between 900 nm and 1100 nm, and the temperature coefficient of the refractive index of the optical element is 9 × 10 ⁻⁶ / ° C. or more in the wavelength band. It is characterized by the following.
According to such an invention, the length of the optical element in the optical axis direction can be made shorter than the length of the space between the semiconductor amplifying element and the optical fiber in the optical axis direction. Then, when the temperature of the base is further changed, the amount of change in the reflection peak wavelength of the grating and the amount of change in the wavelength of the longitudinal mode can be matched.
[0012]
Further, the present invention is characterized in that an end face of the optical element is formed to be convex.
According to such an invention, the end face of the optical element formed to be convex functions as a convex lens. Therefore, since the optical element also serves as a lens for optically coupling with the optical fiber, a more stable laser device can be provided with a simple structure.
[0013]
Further, the present invention is characterized in that the optical fiber is a polarization maintaining optical fiber.
According to such an invention, the output laser light can be converted to linearly polarized light.
[0014]
Further, the present invention is characterized in that a non-reflection coating is applied to the light generated by the semiconductor optical amplifying element on the end face of the optical fiber close to the semiconductor optical amplifying element.
According to such an invention, it is possible to suppress the laser light generated by the optical resonator constituted by the end face of the optical fiber and the light reflecting surface of the semiconductor optical amplifier, and to provide a more stable laser device. .
[0015]
Further, the present invention is characterized in that an end face of the optical fiber close to the semiconductor optical amplifier is cut so as to have a Brewster angle with respect to light generated by the semiconductor optical amplifier.
According to such an invention, it is possible to suppress the laser light generated by the optical resonator constituted by the end face of the optical fiber and the light reflecting surface of the semiconductor optical amplifier, and to provide a more stable laser device. .
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a laser device having a wavelength tunable function according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram of a wavelength tunable laser device according to an embodiment. The apparatus according to the embodiment includes an optical fiber having a semiconductor optical amplifier element 1, a first lens 2, an optical element 3 having a positive temperature coefficient of refractive index, a second lens 4, and a grating 16 (hereinafter referred to as an optical fiber as appropriate). (Referred to as a grating) 5, a base 6, and a Peltier element 7 as temperature control means.
[0017]
The semiconductor optical amplification device 1 is a semiconductor device having a function of generating and amplifying light by injecting a current, and includes a light reflection surface 11 and a light emission surface 12. The light reflecting surface 11 is a surface provided with a high reflection coating such that the reflectance becomes as high as possible with respect to the laser oscillation wavelength, and the light emitting surface 12 is such that the reflectance becomes as low as possible with respect to the laser oscillation wavelength. The surface is coated with an anti-reflective coating.
Light generated inside the semiconductor optical amplifier 1 is emitted from the light emitting surface 12, and light incident from the outside of the semiconductor optical amplifier 1 through the light emitting surface 12 to the inside of the semiconductor optical amplifier 1 is The light passes through the inside, is reflected by the light reflecting surface 11, and is amplified again before being emitted from the light emitting surface 12. The light reflecting surface 11 of the semiconductor optical amplifier 1 forms an optical resonator 17 together with the grating 16.
The first lens 2 is a lens for collimating the light emitted from the semiconductor optical amplifying element 1, and has a non-reflective surface on the surface in order to prevent the reflected light from the lens surface from returning to the semiconductor optical amplifying element 1. Coated.
The second lens 4 is a lens for coupling the light emitted from the semiconductor optical amplifying element 1 and collimated by the first lens 2 to the optical fiber 5. The reflected light from the lens surface returns to the semiconductor optical amplifying element 1. In order to avoid this, the surface is provided with an anti-reflection coating.
[0018]
In the optical fiber 5, a grating 16 for reflecting a specific wavelength is formed in a core portion at an end near the semiconductor optical amplifying element 1. The grating 16 is formed by periodically changing the refractive index of the core of the optical fiber, and its reflection peak wavelength, that is, the wavelength λ at which the reflectance becomes maximum, is expressed by the following equation (1). You.
λ = 2 · n · Λ ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (1)
n: Effective refractive index of grating Λ: Period of grating (m)
Since n and に お け る in equation (1) increase with increasing temperature, the reflection peak wavelength λ also increases with temperature, and its value is about 0.0095 nm / ° C.
However, this value is a value when the reflection peak wavelength is about 900 to 1100 nm. The grating 16 forms an optical resonator 17 together with the light reflection surface 11 of the semiconductor optical amplifier 1.
[0019]
Also, by changing the length of the grating and the magnitude of the change in the refractive index, the reflectance and the bandwidth of the grating 16 can be arbitrarily changed.
Here, the bandwidth refers to a wavelength region where the reflectance is at least half the reflectance of the reflection peak wavelength. This bandwidth is determined as follows.
That is, the laser light is separated from the reflection peak wavelength of the grating 16 by the wavelength interval of the longitudinal mode of the laser light determined by the effective resonator length of the optical resonator 17 composed of the light reflecting surface 11 of the semiconductor optical amplifier 1 and the grating 16. The bandwidth of the grating 16 is determined so that the reflectance at the reflected wavelength is lower than the reflectance at the reflection peak wavelength by 2% or more.
[0020]
By doing so, it becomes possible to selectively oscillate only the longitudinal mode that matches the reflection peak wavelength, and the output laser light can be made into the single mode.
Specifically, when the wavelength of the laser light is 900 nm or more and the distance between the light reflecting surface 11 of the semiconductor optical amplifier 1 and the end of the grating 16 near the semiconductor optical amplifier 1 is set to 20 mm or less, the longitudinal mode of the laser light The wavelength interval is about 0.02 nm or more, and in order to make the reflectance at a wavelength 0.02 nm or more away from the reflection peak wavelength lower by 2% or more than the reflectance at the reflection peak wavelength, the reflection of the grating 16 is required. The bandwidth may be set to 1.5 nm or less.
[0021]
Here, the effective resonator length L of the optical resonator 17 composed of the light reflecting surface 11 of the semiconductor optical amplifier 1 and the grating 16 is represented by the following equation (2).
L = n ₁ · l ₁ + n ₂ · l ₂ + n ₃ · l ₃ + n ₄ · l ₄ + n _air · l _air ‥‥‥ (2)
n ₁ : refractive index of the semiconductor optical amplifier 1 l ₁ : length of the semiconductor optical amplifier 1 in the optical axis direction (m)
n ₂ : refractive index of the first lens 2 l ₂ : length of the first lens 2 in the optical axis direction (m)
n ₃ : refractive index of the optical element 3 l ₃ : length of the optical element 3 in the optical axis direction (m)
n ₄ : refractive index of the second lens l ₄ : length of the second lens in the optical axis direction (m)
n _air : refractive index of _air l _air : total (m) of lengths of air portions inside optical resonator 17 in the optical axis direction
[0022]
The optical element 3 having a positive refractive index temperature coefficient is an element whose refractive index changes when the temperature changes, and the material thereof is synthetic quartz, optical glass such as PBH21, PBH71 or PBH72, LiTaO ₃ , LiNbO _3, or the like. A single crystal such as KNbO ₃ can be used. The surface of the optical element 3 is optically polished and provided with an anti-reflection coating.
The length l of the optical element 3 in the optical axis direction is calculated by Expression (3).
l = L · (dλ / dT) / [λ · (dn / dT)] (m) ‥‥‥‥ (3)
L: Effective resonator length L (m) of the optical resonator 17
dλ / dT: the amount by which the reflection peak wavelength of the grating 16 changes with temperature (m / ° C.)
λ: wavelength of laser light (m)
dn / dT: temperature coefficient of refractive index of optical element 3 (1 / ° C.)
Specifically, when LiTaO ₃ is used as the material of the optical element 3, if the wavelength of the laser beam is 900 to 1100 nm, dn / dT = 6 × 10 ⁻⁵ and dλ / dT = 0.005 nm / ° C. Therefore, the length 1 of the optical element 3 is calculated to be about 0.15 · L.
[0023]
Further, as the material of the optical element 3, a material having a temperature coefficient of refractive index of 9 × 10 ⁻⁶ or less is not used. This is because, when the temperature coefficient of the refractive index is 9 × 10 ⁻⁶ or less, the length 1 of the optical element 3 in the optical axis direction calculated by the equation (3) may be larger than the effective resonator length L. It is.
The base 6 holds the optical element 3, the optical fiber 5, and the second lens 4. The optical element 3, the optical fiber 5, and the second lens 4 are connected to the base 6 in order to easily conduct heat. The heat resistance is fixed so as to be sufficiently small.
The Peltier element 7 is for changing and controlling the temperature of the base 6 installed thereon.
[0024]
Next, the operation of the laser device having the configuration shown in FIG. 1 will be described.
Light generated by injecting a current into the semiconductor optical amplifying element 1 is emitted from the emission surface 12 and collimated by the first lens 2, passes through the inside of the optical element 3, and passes through the optical fiber The light is condensed on the end face of the core portion of No. 5. The light condensed on the end face of the core portion is guided into the core, reflected by the grating 16, and then returned to the semiconductor optical amplifier device 1 through the light exit surface 12 again through the reverse path. Then, the light passes through the inside of the semiconductor optical amplification element 1, is reflected by the light reflection surface 11, and is amplified again before being emitted from the light emission surface 12. By repeating the above operation, laser oscillation is caused between the light reflecting surface 11 and the grating 16.
[0025]
A part of the laser light generated by the laser oscillation is guided through the optical fiber 5 and output to the outside of the optical resonator 17. The semiconductor optical amplifying device 1 has a function of operating in a certain wavelength band between 900 and 1100 nm, and the grating 16 has a reflection peak wavelength within a range of the band in which the semiconductor amplifying device 1 operates. Therefore, laser oscillation occurs in the range of 900 to 1100 nm.
Further, since the distance between the light reflecting surface 11 and the end of the grating 16 is set within 20 mm, the wavelength interval in the longitudinal mode of the laser light is about 0.02 nm or more. The reflection bandwidth of the grating 16 is set to 1.5 nm or less.
By doing so, the reflectivity at a wavelength separated by the wavelength interval of the longitudinal mode of the laser beam becomes lower than the reflectivity at the reflection peak wavelength by 2% or more. Then, reflection loss occurs and oscillation cannot be performed, and the output laser light is in a single mode.
[0026]
This will be described with reference to the characteristic diagram of FIG. Reference numeral 41 denotes a longitudinal mode of the laser light determined by the effective resonator length of the optical resonator 17, and reference numeral 42 denotes a wavelength characteristic of the reflectance of the grating 16.
As described above, the reflectance of the grating 16 decreases symmetrically and symmetrically around the reflection peak wavelength, and when the wavelength bandwidth is 1.5 nm or less, the longitudinal mode 41b adjacent to the longitudinal mode 41a that matches the reflection peak wavelength. In this case, the reflectivity is lower than the peak value by 2% or more, so that laser oscillation cannot be performed, and only the longitudinal mode 41a oscillates.
[0027]
When the temperature of the grating 16 is increased by driving the Peltier element 7, as shown in FIG. 6, the reflection peak wavelength 42a is increased at a rate of about 0.0095 nm / ° C. on the long wavelength side (the direction of the arrow in the figure). Moving.
Here, assuming that the effective resonator length of the optical resonator 17 does not change, the wavelength of the longitudinal mode 41a does not change. Therefore, laser oscillation occurs only when the reflection peak wavelength 42a matches one of the peaks of the longitudinal mode 41. Therefore, the wavelength of the laser beam can be changed only at the same discrete value as the longitudinal mode 41.
In order to avoid such a situation, as shown in FIG. 5, the wavelength of the longitudinal mode 41a is shifted to the longer wavelength side at the same time as the reflection peak wavelength 42a of the grating 16 is shifted to the longer wavelength side. Good.
[0028]
That is, since the effective resonator length is increased by increasing the temperature of the optical element 3 having a positive temperature coefficient of refractive index installed on the base 6, the wavelength of the longitudinal mode 41a moves to the longer wavelength side, In addition, by setting the length of the optical element 3 in the optical axis direction to a value calculated by the equation (3), the rate of the movement may be about 0.0095 nm / ° C.
By driving the Peltier element 7 to raise the temperature of the grating 16, the reflection peak wavelength 42a moves toward the longer wavelength side at a rate of about 0.0095 nm / ° C. as shown in FIG. At the same time, the wavelength of the longitudinal mode 41a also moves toward the longer wavelength side at a rate of about 0.0095 nm / ° C., so that the wavelength of the laser beam can be continuously changed.
[0029]
Next, a specific configuration of the wavelength tunable laser device will be described with reference to FIG.
On the base 9, the semiconductor optical amplifying element 1, the first lens 2, the thermistor 19, and the photodiode 13 mounted on the heat sink 8 are mounted. The base 9 is mounted on a Peltier device 10, and the Peltier device 10 is mounted on a housing 15. In the base 9, the Peltier device 10 is driven such that the temperature detected by the thermistor 19 is kept constant. The light reflecting surface 11 of the semiconductor optical amplifying element 1 transmits a small part of the laser light, and the output of the laser light transmitted through the light reflecting surface is detected by the photodiode 13 and detected by the photodiode 13. The current injected into the semiconductor optical amplifying element 1 is controlled so that the output of the laser light thus emitted becomes constant.
[0030]
The optical element 3 having a positive temperature coefficient of refractive index, the second lens 4, the optical fiber grating 5, and the thermistor 18 are mounted on the base 6. The base 6 is mounted on the Peltier device 7, and the Peltier device 7 is mounted on the housing 15. In the base 6, the Peltier element 7 is driven such that the temperature detected by the thermistor 18 matches the specified temperature. The housing 15 has an airtight structure so that foreign matter does not enter from the outside.
[0031]
Although the optical element 3 having a positive refractive index temperature coefficient has a flat end face in the embodiment of FIG. 2, if the end face of the optical element 3 is formed in a convex shape as shown in FIG. Since the end surface of the third lens 3 functions as a convex lens, it can also function as the second lens 4 in FIG.
Further, a polarization maintaining optical fiber may be used as the optical fiber grating 5.
By doing so, it is possible to eliminate the disturbance of the polarization plane that occurs while the emitted laser light, that is, the output laser light is guided through the optical fiber 5, and more stable laser oscillation becomes possible.
[0032]
Further, the end face 14 of the optical fiber 5 may be provided with a non-reflection coating for the laser beam.
By doing so, it is possible to avoid reflected light that is reflected on the end face 14 of the optical fiber 5 and returns to the semiconductor optical amplifier 1, and more stable laser oscillation becomes possible. Further, the end surface 14 of the optical fiber 5 on the light incident surface side may be cut so as to have a Brewster angle with respect to the laser light.
By doing so, it is possible to prevent the oscillated laser light from being reflected by the end face 14 of the optical fiber 5 and returning to the semiconductor optical amplifier device 1, and more stable laser oscillation becomes possible.
[0033]
In the embodiment, the optical fiber having the optical element and the grating is held (attached) to a single base, and the base is controlled in temperature by a Peltier element. However, the optical fiber having the optical element and the grating is formed. Can be mounted on separate bases for independent temperature control, or the optical element and the optical fiber can be housed in a thermostat to control the temperature.
However, if the optical fiber having the optical element and the grating formed on a single base is held as in the embodiment, there are advantages that the size can be reduced and the temperature control mechanism can be simplified.
[0034]
【The invention's effect】
The wavelength tunable laser device of the present invention is configured as described above, and is provided between the optical fiber and the semiconductor optical amplifying element, and is an optical element having a positive refractive index temperature coefficient that is transparent to light generated by the semiconductor amplifying element. The provision of the element and the temperature control means for controlling the temperatures of the optical fiber and the optical element makes it possible to continuously change the wavelength of the laser.
[0035]
In addition, the semiconductor optical amplifying element operates in a certain wavelength band of 900 nm or more, and the distance between the light reflecting surface of the semiconductor optical amplifying element and the end of the grating closer to the semiconductor optical amplifying device is 20 mm or less. By setting the reflection bandwidth to 1.5 nm or less, laser light output from the laser device can be in a single mode, and a laser useful for application to spectroscopic analysis or the like can be provided.
Further, when the semiconductor optical amplifying element operates in a certain wavelength band between 900 and 1100 nm, and the refractive index temperature coefficient of the optical element is set to 9 × 10 ⁻⁶ / ° C. or more in the wavelength band, it is changed. The amount of change in the reflection peak wavelength of the grating and the amount of change in the wavelength of the longitudinal mode can be matched.
[0036]
In addition, by forming the end face of the optical element into a convex shape, the optical element can also function as a lens that performs optical coupling with an optical fiber, and a more stable laser device is provided by simplifying the structure. it can.
Further, by using a polarization-maintaining optical fiber as the optical fiber, the output laser light can be linearly polarized.
Also, by applying an anti-reflection coating to the light generated by the semiconductor optical amplifying element on the end face of the optical fiber close to the semiconductor optical amplifying device, the end face of the optical fiber and the light reflecting face of the semiconductor optical amplifier are constituted. Laser light generated by the optical resonator can be suppressed, and a laser device capable of oscillating more stable laser light can be provided.
[0037]
In addition, the end face of the optical fiber close to the semiconductor optical amplifier is cut so as to have a Brewster angle with respect to the light generated by the semiconductor optical amplifying element, so that the end face of the optical fiber and the optical reflection of the semiconductor optical amplifier are reduced. It is possible to suppress laser light generated by an optical resonator composed of a surface and a more stable laser device. If the optical element and the optical fiber are held on a single base and the base is controlled by a Peltier element, the size can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a laser device according to an embodiment of the present invention.
FIG. 2 is a sectional view showing a configuration of an embodiment of the laser device of the present invention.
FIG. 3 is a sectional view showing the configuration of another embodiment of the laser device of the present invention.
FIG. 4 is a characteristic diagram showing a relationship between a reflection peak wavelength of a grating and a longitudinal mode of laser light in the laser device of the present invention.
FIG. 5 is a diagram showing a wavelength tunable characteristic of the laser device according to the embodiment of the present invention.
FIG. 6 is a diagram illustrating a wavelength tunable characteristic according to the related art.
[Explanation of symbols]
1: Semiconductor light amplifying element 2: First lens 3: Optical element having a positive refractive index temperature coefficient 4: Second lens 5: Optical fiber 6, 9: Base 7, 10: Peltier element 11: Light reflecting surface 12: Light emitting surface 14: End face of optical fiber 5 (light incidence) 15: Housing 16: Grating 17: Optical resonator 18, 19: Thermistor

Claims (10)

A semiconductor light amplifying element having a function of generating and amplifying light by injecting a current into a light reflecting surface, a light emitting surface, and a region sandwiched between these surfaces; and An optical fiber in which a reflecting grating is formed, and a laser generated by the semiconductor optical amplifier by the optical resonator constituted by the light reflecting surface and the grating, and oscillating the laser outside the optical resonator. A laser device for outputting light,
An optical element that is provided between the optical fiber and the semiconductor optical amplification element, is transparent to light generated by the semiconductor amplification element, and has a positive refractive index temperature coefficient,
A laser device comprising: a temperature control unit that controls the temperatures of the optical fiber and the optical element. 2. The laser device according to claim 1, wherein the optical fiber and the optical element are held by a base, and the temperature control means controls a temperature of the base. The laser device according to claim 1, wherein the optical fiber and the optical element are held on a single base, and the temperature control means controls the temperature of the base. 4. The laser device according to claim 1, wherein said temperature control means is a temperature control element such as a Peltier element. The semiconductor optical amplifying element operates in a certain wavelength band of 900 nm or more, a distance between the light reflecting surface and an end of the grating closer to the semiconductor optical amplifying element is 20 mm or less; 5. The laser device according to claim 1, wherein the reflection device has a reflection bandwidth of 1.5 nm or less and outputs a single mode laser beam. The semiconductor optical amplifying element operates in a certain wavelength band between 900 and 1100 nm, and the temperature coefficient of refractive index of the optical element is 9 × 10 ⁻⁶ / ° C. or more in the wavelength band. The laser device according to claim 1. The laser device according to claim 1, wherein an end surface of the optical element is formed in a convex shape. The laser device according to any one of claims 1 to 7, wherein the optical fiber is a polarization maintaining optical fiber. 9. An anti-reflection coating for light generated by the semiconductor optical amplifier element is provided on an end face of the optical fiber on the side closer to the semiconductor optical amplifier element. The laser device according to claim 1. 10. The optical fiber according to claim 1, wherein an end face of the optical fiber close to the semiconductor optical amplifier is cut so as to have a Brewster angle with respect to light generated by the semiconductor optical amplifier. The laser device according to any one of the above.

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