WO2014156544A1

WO2014156544A1 - Onboard ignition device combining semiconductor laser light source and solid-state laser device

Info

Publication number: WO2014156544A1
Application number: PCT/JP2014/055829
Authority: WO
Inventors: 常包　正樹; 拓範平等; 金原　賢治
Original assignee: 大学共同利用機関法人自然科学研究機構; 株式会社デンソー
Priority date: 2013-03-26
Filing date: 2014-03-06
Publication date: 2014-10-02
Also published as: JP6245629B2; JP2014192166A

Abstract

[Problem] To provide a laser device for emitting pulse laser light over the entire range of ambient temperature between 20°C and 80°C. [Solution] There is a need for pulse laser light to be emitted over the entire range between 20°C and 80°C in order to achieve a device capable of igniting the fuel supplied to an engine with the pulse laser light emitted from a solid-state laser medium excited by semiconductor laser light emitted from a semiconductor laser light source. The operation temperature range is insufficient in the current laser device. Thus, an yttrium aluminum garnet containing neodymium is selected as the solid-state laser medium, and the semiconductor laser light source is provided with an array element where vertical-cavity surface-emitting laser elements having multilayered films formed on both sides of an active layer are arrayed two-dimensionally, the semiconductor laser light source being selected to have a central oscillation wavelength of 804.0 nm to 805.5 nm at 20°C and have a temperature dependency of 0.07 nm/°C or less at the central oscillation wavelength.

Description

In-vehicle ignition system combining a semiconductor laser light source and a solid-state laser device

This specification discloses an apparatus that combines a semiconductor laser light source and a solid-state laser device. In this combination device, a semiconductor laser light source emits semiconductor laser light, and a solid-state laser device excited by the semiconductor laser light emits solid-state laser light. In this specification, a semiconductor laser light source and a solid-state laser device are provided, the semiconductor laser light emitted from the semiconductor laser light source enters the solid-state laser medium, and the solid-state laser medium excited by the semiconductor laser light emits the solid-state laser light. The entire radiating device is called a “solid laser device excited by semiconductor laser light”. Hereinafter, for simplification, it is simply abbreviated as “laser device”.
The present specification discloses a technique for extending the operating temperature range of the laser device. In particular, a technique for extending the operating temperature range necessary to realize a device for igniting fuel supplied to an engine by the laser device is disclosed.
In this specification, laser light emitted from a semiconductor laser light source is referred to as semiconductor laser light, and laser light emitted from a solid laser medium is referred to as solid laser light. Both are laser beams.

FIG. 15 shows the configuration of the laser device disclosed in Non-Patent Document 1. In FIG. 15, reference numeral 101 indicates an array element (an example of a semiconductor laser light source) in which a plurality of vertical cavity surface emitting laser elements (VCSEL) are arranged along a two-dimensional matrix, and reference numeral 105 indicates a collimator. Reference numeral 106 denotes a condenser lens, reference numeral 110 denotes yttrium aluminum garnet (Nd: YAG) containing neodymium, and reference numeral 111 denotes yttrium aluminum garnet (Cr) containing chromium. : YAG), reference numeral 115 indicates a Brewster plate, and reference numeral 112 indicates an output mirror. Nd: YAG110 has a rod shape, and a dielectric coat film 110a having a high transmittance with respect to 808 nm and a high reflectance with respect to 1064 nm is formed on the end face on which the semiconductor laser light is incident. The output mirror 112 includes a film 112a having a reflectivity of 90% with respect to 1064 nm. Nd: YAG110 is a solid-state laser medium that is excited to emit solid-state laser light when irradiated with semiconductor laser light. An Nd: YAG solid-state laser resonator is formed by an optical device located between the dielectric coat film 110a and the film 112a.

The array element 101 emits semiconductor laser light controlled to a wavelength of 808 nm. The semiconductor laser light is condensed on the end face of the Nd: YAG 110 by the two

lenses

105 and 106. The semiconductor laser light condensed on the end face of the Nd: YAG 110 is incident on the Nd: YAG 110 and absorbed. Nd: YAG110 becomes a solid laser medium. The Cr: YAG 111 inserted in the resonator operates as a passive Q switch and emits pulsed laser light. The Brewster plate 115 controls the pulse laser beam to linearly polarized light.

In order to control the temperature of the array element 101, the array element 101 is mounted on a diamond heat spreader, the heat spreader is mounted on a copper heat sink, and the heat sink is cooled by an electronic cooling device. The array element 101 is controlled by an electronic cooling device to a temperature at which the wavelength of the semiconductor laser light emitted from the array element 101 is 808 nm.

FIG. 16 shows a semiconductor laser light source disclosed in Non-Patent Document 2. The semiconductor laser light source emits semiconductor laser light that excites the fiber laser 140. Reference numeral 101 represents a VCSEL array element, reference numeral 130 represents a microlens array for individually collimating semiconductor laser light emitted from each light emitting point of the VCSEL array element 101, and reference numeral 106 represents a semiconductor. A condensing lens for condensing the laser beam 107 on the end face of the fiber 140 is shown.

The array element 101 emits semiconductor laser light having a wavelength of 976 nm. In order to control the temperature of the array element 101, the array element 101 is mounted on a diamond submount 102, and the submount 102 is mounted on a copper water-cooled microchannel heat sink to control the temperature. The array element 101 is adjusted to a temperature at which the wavelength of the semiconductor laser light to be emitted becomes 976 nm.

FIG. 17 shows a semiconductor laser light source disclosed in Non-Patent Document 3. The semiconductor laser light source emits semiconductor laser light that excites the fiber laser 140. Reference numeral 101 denotes an array element of a vertical cavity surface emitting laser (VCSEL), reference numeral 131 denotes an external mirror, and reference numeral 130 denotes a micro that individually collimates semiconductor laser light from each light emitting point of the array element 101. An array of lenses is shown, and reference numeral 106 denotes a condenser lens. The array element 101 emits semiconductor laser light having a wavelength of 976 nm. By providing the mirror 131 outside the VCSEL, it is possible to effectively increase the resonator length of the array element 101 of the VCSEL, thereby narrowing the emission angle of the semiconductor laser light emitted from the array element 101 and increasing the luminance. Goes up. Compared to the configuration of FIG. 16 in which the mirror is built in the VCSEL, the semiconductor laser light can be efficiently incident on the optical fiber having a small core.
In order to control the temperature of the VCSEL array 101, the array element 101 is mounted on a diamond submount 102, and the submount 102 is mounted on a copper block and cooled. The array element 101 is controlled to a temperature at which the wavelength of the semiconductor laser light emitted from the array element 101 is 976 nm.

In recent years, with the improvement of the performance of the laser device, the spread to physics and chemistry or industrial use has progressed, but in order to further promote the spread to a wide range of industrial and consumer applications, the operating temperature range of the laser device has been increased. Expansion is an issue. For example, when mounted on an automobile, it is required to operate stably in a temperature range from 20 ° C to 80 ° C. Although the environmental temperature in which the automobile is used is wider than the above temperature range, it requires less power to heat the laser device than to cool the laser device. The laser device operates stably in a temperature range from 20 ° C. to 80 ° C. because of the fact that the device itself generates heat and it is possible to provide an air cooling device that cools the laser device with a cooling fan. If possible, the laser device can be mounted on the vehicle.

The temperature dependence of the oscillation center wavelength of a semiconductor laser light source exists. The oscillation center wavelength of the semiconductor laser light source is uniquely determined by the band gap of the semiconductor active layer. However, since the band gap changes depending on the temperature, the oscillation center wavelength of the semiconductor laser light source changes depending on the temperature. In the case of a normal semiconductor laser light source, when the environmental temperature rises by 1 ° C., the oscillation center wavelength becomes longer by 0.3 nm. On the other hand, the absorption band of the solid laser medium is relatively narrow. In the case of Nd: YAG, as shown in FIG. 10, there is a strong absorption band A at 807.0 to 809.5 nm. This means that when the operating temperature changes by 8 ° C., the oscillation center wavelength of the semiconductor laser light source changes from the shortest wavelength 807.0 nm of the absorption band A of the solid laser medium to the longest wavelength 809.5 nm. To do. The operating temperature range of the conventional laser apparatus is only 8 ° C.

Therefore, in the case of the conventional laser apparatus, a semiconductor laser light source is selected in which the wavelength of the semiconductor laser light at a specific operating temperature is in the vicinity of 808 nm, which is the maximum absorption coefficient even in the absorption band A, and the semiconductor laser light source is An electronic cooling device or a water cooling type cooling device that maintains the operating temperature is used in combination.

In order to mount the laser device on the vehicle, air cooling is not sufficient, and if an electronic cooling device or a water-cooled cooling device is required, it becomes difficult to mount the laser device on the vehicle. Opportunities for enjoying the merits of the laser device will be greatly reduced.

The present specification discloses the above laser device that does not require an electronic cooling device or a water-cooled cooling device, and can be mounted on the vehicle by being used together with a simple heating device or a simple air-cooling device.
In particular, a technique for realizing an ignition device that ignites fuel supplied to an engine with pulsed laser light emitted from the laser device is disclosed.
In the present specification, if the above laser device that operates stably in a temperature range of 20 ° C. to 80 ° C. is obtained, it is not necessary to use an electronic cooling device or a water-cooled cooling device. Disclosed is the above laser device or an ignition device using the laser device, which has been created based on the knowledge that it can be mounted on the vehicle when used in combination with an air cooling device.

In the technique described in this specification, the following two findings are used in combination.
(First Knowledge) The oscillation center wavelength of the semiconductor laser light source is uniquely determined by the band gap of the semiconductor active layer, but is not determined only by it, and is also affected by the reflection characteristics of the mirrors constituting the resonator. Therefore, a VCSEL using a semiconductor multilayer film for mirrors disposed on both sides of the semiconductor active layer and using distributed Bragg reflection has been developed. According to this VCSEL, the temperature dependence of the oscillation center wavelength is reduced to 0.07 nm / ° C. For example, the temperature dependence of the oscillation center wavelength of a VCSEL provided by Princeton Optronics, Inc. (1 Electronics Drive, Mercerville, New Jersey 08619, USA) is 0.07 nm / ° C.
(Second Knowledge) The conventional laser device uses the absorption band A shown in FIG. 10, but actually has an absorption capability even in the wavelength band B adjacent thereto, and the absorption band A and the absorption band B Can be used as a whole. Although the absorption coefficient in the absorption band B is lower than that in the absorption band A, it has not been used so far, but it is possible to oscillate solid laser light.

When the entire absorption band A and absorption band B are used, the absorption band expands to 803.0 to 809.5 nm. That is, it has a wavelength width of 6.5 nm. When used in combination with the above-described semiconductor laser light source having a temperature dependency of 0.07 nm / ° C., an operating temperature range of 90 ° C. or higher can be secured.

The laser device disclosed in the present specification is obtained by the above consideration and wavelength determination experiment,
(1) Yttrium aluminum garnet (Nd: YAG) containing neodymium is used as the solid laser medium.
(2) As the semiconductor laser light source, an array light source in which vertical cavity surface emitting laser elements (VCSEL) in which a multilayer film is formed on both sides of the active layer is two-dimensionally arranged is used. In particular, a semiconductor laser light source having an oscillation center wavelength of 804.0 to 805.5 nm at 20 ° C. and a temperature dependency of the oscillation center wavelength of 0.07 nm / ° C. or less is used.

The vertical axis in FIGS. 11 to 13 shows the ratio of the excitation light energy radiated from the semiconductor laser light source at 20 ° C. to the energy absorbed in the solid laser medium (the latter value when the former is 1). . The amount of power applied to the semiconductor laser light source was kept constant regardless of the environmental temperature. When the environmental temperature changes, the wavelength of the semiconductor laser light emitted from the semiconductor laser light source changes (therefore, the absorption coefficient shown in FIG. 10 changes), and the energy of the semiconductor laser light also changes. The vertical axis shows the effective absorption ratio taking into account two effects. Hereinafter, for convenience, it is referred to as an effective absorption coefficient. The vertical axis in FIGS. 11 to 13 shows the measurement results of the temperature dependence of the effective absorption coefficient of Nd: YAG having a length of 4 mm.
FIG. 11 shows a case where a semiconductor laser light source having an oscillation center wavelength of 803.0 nm at 20 ° C. and a case where a semiconductor laser light source of 803.5 nm is used. In the case of FIG. 11, the wavelength of the semiconductor laser light when the environmental temperature is low is too short compared to the shortest wavelength of the absorption band B, and the effective absorption coefficient when the environmental temperature is low is reduced.
FIG. 13 shows a case where a semiconductor laser light source with an oscillation center wavelength of 806.0 nm at 20 ° C. is used and a case where a semiconductor laser light source of 806.5 nm is used. In the case of FIG. 13, the wavelength of the semiconductor laser light when the environmental temperature is high is too long compared to the longest wavelength of the absorption band A, and the effective absorption coefficient when the environmental temperature is high is lowered.
FIG. 12 shows the effective absorption coefficient when using a semiconductor laser light source with oscillation center wavelengths of 804.0 nm, 804.5 nm, 805.0 nm, and 805.5 nm at 20 ° C. In the case of FIG. 12, the wavelength is not too short even when the environmental temperature is low, and the wavelength is not too long when the environmental temperature is high, and an effective absorption coefficient of 40% or more is obtained in the entire temperature range of 20 ° C. to 80 ° C. It can be seen that it can be secured.
FIG. 14 shows the result of obtaining the value of “maximum effective absorption coefficient within 20 to 80 ° C./minimum effective absorption coefficient within 20 to 80 ° C.” from the effective absorption coefficients shown in FIGS. It can be seen that when the oscillation center wavelength at 20 ° C. is in the range of 804.0 to 805.5 nm, the value of the ratio is suppressed to less than 2.0.

When mounting the above laser equipment, an effective absorption coefficient of 40% or more can be secured over the entire temperature range of 20 to 80 ° C, and the maximum effective absorption coefficient within 20 to 80 ° C / minimum effective absorption within 20 to 80 ° C. If the value of the coefficient ratio is 2.0 or less, there is no need to use an electronic cooling device or a water-cooling type cooling device, and the degree of use together with a simple heating device, a simple air-cooling type cooling device, or a simple output adjustment circuit. It has been confirmed that the vehicle can be mounted on the vehicle by this measure. According to the laser device disclosed in this specification (more precisely, a solid-state laser device excited by semiconductor laser light), it can be mounted in a practical sense. It is possible to mount an ignition device that ignites fuel with pulsed laser light emitted from a solid laser medium.

In the technique disclosed in this specification, in order to use the absorption band B having a low absorption coefficient, it is preferable to use it together with a technique for increasing the absorption coefficient of Nd: YAG. In order to improve the absorption coefficient, it is desirable to increase the Nd concentration. However, in the case of single crystal YAG, it is known that the laser characteristics are remarkably deteriorated when the Nd concentration exceeds 1.1 at%. In the case of polycrystalline YAG that has recently been put into practical use, it is known that even if the Nd concentration is increased to about 2.0 at%, the laser characteristics are hardly deteriorated.
Therefore, it is effective to use polycrystalline Nd: YAG containing 1.1 to 2.0 at% neodymium as the solid-state laser medium.

Polycrystalline Nd: YAG and polycrystalline Cr: YAG can be produced by sintering, and a ceramic production method can be applied. By applying the ceramic manufacturing method, a rod in which Nd: YAG and Cr: YAG are integrated can be easily manufactured. When a rod in which Nd: YAG and Cr: YAG are integrated is used, the number of optical elements constituting the pulse laser beam emitting device can be reduced, the pulse laser beam emitting device can be reduced in size, and vibration can be achieved. It is possible to realize a pulse laser light emitting device that is strong against the above.
When using an optical element in which Cr: YAG is bonded to the end surface of Nd: YAG, one end surface of Nd: YAG and one end surface of Cr: YAG are bonded, and the non-bonded end surface of Nd: YAG and Cr: The non-joint surface of YAG is made parallel. When semiconductor laser light is incident on the non-joint end surface of Nd: YAG, a relationship in which pulse laser light is emitted from the non-joint surface of Cr: YAG can be obtained.

If a concave surface is formed on the output mirror of the solid-state laser resonator, the solid-state laser light is not concentrated at the center of the beam, and the laser medium and the output mirror are less likely to be damaged and the operation is stabilized.
Therefore, it is preferable that a concave surface having a radius of 0.5 to 2 mm is formed on the non-bonding surface of Cr: YAG.
In this case, it is preferable that the center of the concave surface is on the central optical axis of Nd: YAG.

It is possible to connect the semiconductor laser light source and the solid laser medium with an optical fiber. When an optical fiber is used, the semiconductor laser light source and the solid laser medium can be arranged separately. The characteristics of the fixed laser medium are difficult to change depending on the temperature, whereas the characteristics of the semiconductor laser light source are likely to change depending on the temperature. Therefore, for example, a technique is effective in which a solid laser medium is arranged in an engine room where the temperature changes greatly, a semiconductor laser light source is arranged in a vehicle compartment where the temperature change width is relatively small, and both are connected by an optical fiber.

The VCSEL has a plurality of light emitting points. As shown in FIGS. 16 and 17, when the semiconductor laser light emitted from each light emitting point is collimated by a microlens, the semiconductor laser light is condensed in a small range. Can do. In addition, as shown in FIG. 17, if a mirror constituting a resonator for semiconductor laser light is provided outside the VCSEL, the emission angle range of the semiconductor laser light can be narrowed. If the above microlens array and the above mirror are integrally formed, the number of necessary parts can be reduced.
Therefore, a microlens array in which microlenses that individually collimate the semiconductor laser light emitted from each light emitting point of the VCSEL are two-dimensionally arranged, and a mirror / microlens array in which a reflective film is integrally formed are used as a VCSEL. And a structure arranged between Nd: YAG. When an optical fiber is used, a structure in which a mirror / microlens array is arranged between the VCSEL and the optical fiber can be used.

When using a microlens array, it is preferable to fix the microlens array and the VCSEL with an ultraviolet curable resin having a curing shrinkage rate of 2% or less. When an ultraviolet curable resin having a curing shrinkage rate of 2% or less is used, adverse effects due to a change in the distance between the VCSEL and the microlens can be avoided when the resin cures and shrinks.

Although a vehicle-mounted ignition device can be realized by the laser device described in this specification, the application is not limited to the ignition device. The pulsed laser beam radiation device itself having a wide operating temperature range has utility.

According to the laser device described in the present specification, a pulse laser radiation device that emits pulse laser light in the entire temperature range of 20 to 80 ° C. and has a small change width of the radiation energy of the pulse laser light is obtained. . Therefore, the laser device can be mounted on the vehicle, and a vehicle-mounted ignition device that ignites fuel by the laser device can be realized. It is possible to increase the combustion efficiency in the engine, improve the fuel consumption, and make the exhaust gas harmless.

The structural example of the said laser apparatus of 1st Example is shown. The structural example of the said laser apparatus of 2nd Example is shown. The structural example of the said laser apparatus of 3rd Example is shown. The structural example of the said laser apparatus of 4th Example is shown. The structural example of an excitation optical system is shown. The fixing method of a micro lens array and VCSEL is illustrated. A method of fixing the mirror / microlens array and the VCSEL is illustrated. The photograph of VCSEL before microlens array fixation and VCSEL after microlens array fixation is shown. The structural example of the said laser apparatus of 5th Example is shown. The figure explaining the absorption band of Nd: YAG. The temperature dependence of the effective absorption coefficient when the oscillation center wavelength at 20 ° C. is 803.5 mm or less is shown. The temperature dependence of the effective absorption coefficient when the oscillation center wavelength at 20 ° C. is 804.0 to 805.5 mm is shown. The temperature dependence of the effective absorption coefficient when the oscillation center wavelength at 20 ° C. is 806.0 mm or more is shown. The relationship between the change ratio of the effective absorption coefficient and the oscillation center wavelength at 20 ° C. is shown. The structure (the 1) of the conventional semiconductor laser excitation optical system is shown. The structure (the 2) of the conventional semiconductor laser excitation optical system is shown. The structure (the 3) of the conventional semiconductor laser excitation optical system is shown.

The features of the embodiments described below are listed first.
(Embodiment 1) A semiconductor laser light source is arranged in the vehicle compartment, a solid laser medium is arranged in the engine room, and both are connected by an optical fiber.
(Mode 2) A heating device is added to the semiconductor laser light source and heated to 20 ° C. or higher when cold.
(Mode 3) Cooling air from a cooling fan is applied to the semiconductor laser light source to suppress the temperature to 80 ° C. or lower.
(Embodiment 4) An electronic cooling device and a water cooling type cooling device are not added to the semiconductor laser light source.

Examples will be described in detail below. FIG. 1 shows a configuration example of the laser apparatus of the first embodiment.
Reference numeral 1 denotes an array element (semiconductor laser light source) in which a plurality of vertical cavity surface emitting lasers (VCSEL) are arranged along a two-dimensional matrix on one plane. The submount 2 is further mounted on a copper heat sink 3. The heat sink 3 is screwed and fixed to the chassis 20 with a highly heat conductive sheet 21 interposed therebetween. The VCSEL array element 1 is not provided with an electronic cooling device, and is not provided with a water-cooling cooling device. The array element 1 of the VCSEL is kept at 80 ° C. or less by transferring heat to the chassis 20. If necessary, the VCSEL array element 1 can be kept at 80 ° C. or lower by providing a simple cooling fan. Further, the VCSEL array element 1 can be kept at 20 ° C. or higher by using it together with a simple heating device.

The array element 1 of the VCSEL has a semiconductor multilayer film formed on both sides of a semiconductor active layer mainly composed of GaAs, and the oscillation center wavelength of the array element 1 is determined by the band gap of GaAs and the reflection characteristics of the semiconductor multilayer film. In the present example, a VCSEL having a temperature dependence of the oscillation center wavelength of 0.07 nm / ° C. and an oscillation center wavelength of 204.0 ° C. at 804.0 to 805.5 nm was selected.

The array element 1 includes a plurality of light emitting points, and semiconductor laser light is emitted from each light emitting point. In the first embodiment, the semiconductor laser light emitted from each light emitting point is collimated by a common collimating lens 5 and is collected by a condensing lens 6 with an Nd: YAG rod 10 (Nd concentration is 1.1 at%, outer diameter is 5 mm, The light is condensed on the end face having a length of 4 mm. On the central optical axis 13 of the Nd: YAG rod 10, Cr: YAG saturable absorber 11 (Cr ⁴⁺ : YAG, outer diameter is 5 mm, length is 3 mm, initial transmittance at 1064 nm is 30%), and made by BK7 Flat output mirrors 12 are arranged.
A coating film having a transmittance of 99% or more with respect to a wavelength of 803 to 810 nm is formed on both end faces of the

lenses

5 and 6. The semiconductor laser beam condensed by the condenser lens 6 is incident on the left end face of the Nd: YAG rod 10. A coating film 10a having a reflectance of 99.7% or more with respect to 1064 nm (the wavelength of pulsed laser light described later) and a transmittance of 95% or more with respect to 803 to 810 nm is formed on the incident end face. ing. On the end face of the output mirror 12, a coating film 12a having a reflectance of 50% with respect to a wavelength of 1064 nm is formed. A resonator for 1064 nm is formed by the

coating films

10a and 12a. A coating film having a transmittance of 99% or more with respect to 1064 nm is formed on the right end face of the Nd: YAG rod 10, both end faces of Cr: YAG 11, and the right end face of the output mirror 12. The efficiency is increased by reducing the light loss of the entire device.
When the semiconductor laser light condensed by the condenser lens 6 is incident on the left end face of the Nd: YAG rod 10, the semiconductor laser light is absorbed by the Nd: YAG rod 10 and the Nd: YAG rod 10 is excited. . As a result, the pulse laser beam 14 is emitted from the output mirror 12 to the outside of the resonator. The pulsed laser light has a high energy density and ignites the fuel supplied into the engine.

(Second embodiment)
FIG. 2 shows a configuration example of the laser apparatus of the second embodiment. Hereinafter, only differences from the first embodiment will be described, and redundant description will be omitted. Reference numeral 1 is a VCSEL array element, in which a plurality of light emitting points are arranged along a two-dimensional matrix, and an oscillation center wavelength at 20 ° C. is selected from 804.0 to 805.5 nm. Yes. Reference numeral 30 is a microlens array in which microlenses for collimating semiconductor laser light emitted from the light emitting points of the array element 1 of the VCSEL are arranged along a two-dimensional matrix. The microlens array 30 has a plurality of microlenses formed on one side of a glass substrate. The arrangement positions of the light emitting points coincide with the arrangement positions of the microlenses, and the semiconductor laser light emitted from one light emitting point enters each microlens. The microlens array 30 is arranged at a position closer to the array element 1 than a position where semiconductor laser beams from two adjacent light emitting points overlap. According to the microlens array 30, it is possible to reduce the condensing diameter of the excitation light in the Nd: YAG rod 10 as compared with the case where the single lens 5 shown in FIG. The threshold value can be lowered and the energy density of the pulsed laser beam can be increased. Moreover, since the distance can be narrowed for a long time, the overlap with the solid laser beam can be increased, and the excitation efficiency and the oscillation light rate can be increased. On both end faces of the microlens array 30, a coating having a transmittance of 99% or more with respect to semiconductor laser light having a wavelength of 803 to 810 nm is formed.

(Third embodiment)
FIG. 3 shows a configuration example of the laser apparatus of the third embodiment. Only the differences from the second embodiment will be described below. In the third embodiment, the semiconductor laser light emitted from the semiconductor laser light source is guided to the solid laser medium 51 using the optical fiber 40. Further, a composite rod 50 in which a polycrystalline Nd: YAG rod 51 and a polycrystalline Cr: YAG rod 52 are integrated is used.
In the third embodiment, the semiconductor laser light is condensed on the end face of the optical fiber 40 by the condenser lens 6. The core diameter of the optical fiber 40 is 0.8 mm, the NA is 0.22, and the length is 3 m. The semiconductor laser light emitted from the other end face of the optical fiber 40 is collimated by the lens 41 and then condensed on the end face of the composite rod 50 by the condenser lens 42.
The composite rod 50 is obtained by integrating a polycrystalline Cr: YAG rod 52 with a polycrystalline Nd: YAG rod 51. The polycrystalline Nd: YAG rod 51 is a kind of ceramic and is manufactured by firing. The polycrystalline Cr: YAG rod 52 is also a kind of ceramic and is manufactured by firing. When firing the Cr: YAG rod 52, the Nd: YAG rod 51 and the Cr: YAG rod 52 are integrated. The Nd concentration of the Nd: YAG rod 51 is 1.5 at%, the outer shape is 5 mm, and the length is 4 mm. Cr ⁴⁺ is added to the Cr: YAG rod 52, the initial transmittance is 30%, the outer shape is 5 mm, and the length is 3 mm. The left end surface (Nd: non-joint surface of YAG rod 51) and the right end surface (Cr: YAG rod 52 non-joint surface) of composite rod 50 are polished to a parallel plane with high accuracy. On the non-joint surface of the Nd: YAG rod 51, a coating film 50a having a reflectance of 99.7% or more with respect to 1064 nm and a transmittance of 95% or more with respect to 803 to 810 nm is formed. On the non-joint surface of the Cr: YAG rod 52, a coating film 50b having a reflectance of 50% with respect to 1064 nm is formed. A resonator for 1064 nm is formed by the

coating films

50a and 50b, and the pulsed laser light 14 is emitted from the coating film 50b to the outside of the resonator. The Nd concentration of the polycrystalline Nd: YAG rod 51 can be increased to 2.0 at%, and when it is increased, the effective absorption coefficient can be increased as a whole (over a wavelength of 803 to 810 nm).

(Fourth embodiment)
FIG. 4 shows a configuration example of the laser device of the fourth embodiment. Only the differences from the third embodiment will be described below.
In the fourth embodiment, an external mirror 31 is provided outside the array element 1 of the VCSEL. A microlens array is integrated with the external mirror 31. The external mirror 31 is made of synthetic quartz, and a dielectric reflection film having a reflectivity of 90% with respect to a wavelength of 803 to 810 nm is formed on the surface of the VCSEL array element 1 side, and a microscopic surface is formed on the opposite surface. A lens array is formed.
FIG. 5 illustrates the positional relationship and functions of the light emitting point 1a, the external mirror 31, and the microlens 31b. A reflective film 31a is formed on the surface of the external mirror 31 on the array element 1 side. The reflective film 31a is parallel to the reflective film formed in the VCSEL, and the reflective film 31a and the reflective film built in the VCSEL constitute a resonator. When a resonator is configured by the reflective film 31a outside the VCSEL and the reflective film in the VCSEL, the length of the resonator is significantly longer than when the resonator is configured by two reflective films in the VCSEL. The radiation angle of the semiconductor laser light emitted from the semiconductor laser light source is reduced, and the beam condensing property is improved. The emitted semiconductor laser light propagates through the external mirror 31, reaches the microlens 31b, and is collimated by the microlens 31b. The numbers and positions of the light emitting points 1a and the microlenses 31b correspond to 1: 1. 4 and 5 are the same as those in FIG. 3 in that each light emitting point is collimated. However, since the resonance length is longer than in FIG. The beam diameter after being focused by 6 is reduced, and semiconductor laser light can be introduced into a fiber having a thinner core.
In the case of FIG. 5, a reflective film is formed on both sides of a semiconductor active layer in the VCSEL, a resonator is formed by two reflective films in the VCSEL, and a reflective film 31a outside the VCSEL and a reflective film in the VCSEL (active A resonator can be formed by a reflective film located on the opposite side of the reflective film 31a as viewed from the layer. The former resonator can regulate the oscillation wavelength of the semiconductor laser light, and the latter resonator can regulate the radiation angle of the semiconductor laser light. The temperature dependence of the oscillation center wavelength can be suppressed to 0.07 nm / ° C. or less while using an external mirror.

(Fixed structure of micro lens array)
FIG. 6 shows a structure for fixing the microlens array 30 shown in FIG. 2 to the array element 1 of the VCSEL. The microlens array 30 is aligned so as to be opposed to each light emitting point position of the array element 1 (that is, the light emitting point of the VCSEL and the optical axis position of the microlens are aligned), and the distance between them is the semiconductor after passing through the microlens. After adjusting so that the laser beam is collimated, a small amount of ultraviolet (UV) curable resin adhesive 60 is inserted into three corners between the array element 1 and the microlens array 30 and irradiated with UV light. The microlens array 30 is fixed to the array element 1 of the VCSEL. For example, a microlens array in which a microlens having a focal length of 0.1 mm is formed is fixed at a position about 0.1 mm away from the array element 1. When an ultraviolet curable resin adhesive having a shrinkage rate of 2% or less by UV irradiation is used, it is possible to avoid the resin from shrinking during curing and changing the distance between the array element 1 of the VCSEL and the microlens array 30. For UV curable adhesives with a shrinkage rate of 2% or less, use, for example, 3555 from EMI, NT-01UV from NITTO DENKO, NOA61 from NORLAND, or AT4291F or AT9290F from NTT Advanced Technology Can do. When the microlens array 30 is directly fixed to the semiconductor substrate of the array element 1 with an ultraviolet curable resin as in this embodiment, the positional shift with respect to the temperature change is only the influence of the temperature expansion and contraction of the adhesive 60, and the submount 2 and others Therefore, stable operation can be obtained over a wide temperature range. Further, since no special base, holder, or fixing space for fixing the microlens array 30 is required, the number of parts is reduced, and the cost can be reduced and the size can be reduced.

(Fixed structure of external mirror with microlens array)
FIG. 7 shows a structure for fixing the external mirror 31 with the microlens array shown in FIGS. 4 and 5 to the array element 1. Also in the embodiment of FIG. 7, the external mirror 31 and the array element 1 are fixed by the ultraviolet curable resin adhesive 60.

The left side of FIG. 8 shows a photograph of the array element 1 before fixing the microlens array 30, and the right side shows a photograph after fixing the microlens array 30. In FIG. 8, an adhesive is inserted into four corners of a 5 mm square microlens array 30, and the semiconductor substrate constituting the array element 1 and the microlens array 30 are fixed.

(5th Example)
FIG. 9 shows a configuration example of the laser apparatus of the fifth embodiment. Only the differences from the fourth embodiment shown in FIG. 4 will be described below.
A concave surface having a radius of 1 mm is processed on the non-bonding end face (pulse laser light emission surface) of Cr: YAG, and a coating film 55b having a reflectance of 50% with respect to light having a wavelength of 1064 nm is formed. 55a and 55b form a resonator 55 for 1064 nm. The center point of the concave surface is on the central optical axis 13 of Nd: YAG51. The pulse laser beam 14 is radiated to the outside of the resonator from the end face where the coating film 55b is formed.
If a concave surface is formed on the non-bonded end surface of Cr: YAG (pulse laser beam radiation surface), the laser beam does not concentrate at the center of the beam, and damage to the solid laser medium and output mirror is unlikely to occur. The radius of the concave surface is preferably in the range of 0.5 to 2 mm.

The present invention is not limited to the above-described embodiments, and can be variously modified with respect to the configurations illustrated in FIGS. 1 to 9 as a final form that operates integrally as a solid-state laser module. For example, various modifications can be made to individual part shapes, types, and reflectance of the coating film, and these are not excluded from the scope of the present invention. The condensing lens as the excitation optical system is appropriately selected from the core diameter of the semiconductor laser element for excitation or the optical fiber and the necessary condensing beam diameter. One condenser lens may be arranged, or a plurality of condenser lenses may be arranged in series.
In the embodiment of the present invention, Cr: YAG is used as the optical switch element in the laser resonator, but Co: Spinal, V: YAG, or SAM which is a semiconductor material may be used. An active Q switch element, a polarization control element, a lens, or the like may be inserted. Of course, only the solid laser medium Nd: YAG may be used. Appropriate optical elements according to the required functions can be inserted into the resonator in the required number and in the required order.
The material of the submount 2 is not limited to SiC, and metals and ceramics having a high thermal conductivity close to that of the VCSEL array element 1, such as CuW, diamond, BeO, and AlN, can be applied. The material of the heat sink 3 is not limited to copper, and a metal or ceramic with high thermal conductivity such as CuW, aluminum, or AlN can be used. For the highly heat-conductive sheet 21, for example, a graphite sheet manufactured by Panasonic Device Co., Ltd., a thermostar manufactured by Takeuchi Kogyo Co., Ltd., a heat conductive phase change sheet manufactured by Shin-Etsu Chemical Co., Ltd., a heat-dissipating silicone rubber made by Shin-Etsu Silicone, etc. Can do. The chassis 20 may be, for example, a metal body of an automobile, a housing of a laser device, or a wall of a building. Or only a metal block may be sufficient, and the fin for cooling and the fan of cooling may be attached there. Since it is not necessary to control and fix the semiconductor laser element at a specific temperature, any chassis may be used as long as the heat generated by the semiconductor laser element has a heat capacity that can be exhausted.

In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

1: Vertical cavity surface emitting laser (VCSEL) array element. The one whose oscillation center wavelength at 20 ° C. is 804.0 to 805.5 nm is selected.
2: Submount 3: Heat sink 5: Lens (for collimation)
6: Lens (for condensing)
7: Semiconductor laser light (excitation light)
10: Nd: YAG rod 10a: Coating film 11: Cr: YAG
12: Output mirror 12a: Coating film 13: Solid laser optical axis 14: Pulse laser light: Solid laser output light 20: Chassis 21: High thermal conductivity sheet 30: Micro lens array 31: External mirror (with micro lens array)
31a: coating film 31b: microlenses 40, 45: optical fiber 41: lens (for collimation)
42: Lens (for condensing)
50:

Composite rods

50a, 50b: Coating film 51: Polycrystalline Nd: YAG (ceramic)
52: Polycrystalline Cr: YAG (ceramic)
55:

Composite rods

55a, 55b: Coating film 56: Polycrystalline Nd: YAG (ceramic)
57: Polycrystalline Cr: YAG (ceramic)
60: Ultraviolet (UV) curable resin adhesive 101: VCSEL array element. The temperature is adjusted to a temperature at which semiconductor laser light having a wavelength of 808 nm is emitted.
102: Submount (heat spreader)
105: Lens (for collimation)
106: Lens (for condensing)
107: Semiconductor laser light: Excitation light 110: Nd: YAG rod 110a: Coating film 111: Cr: YAG
112: Output mirror 112a: Coating film 113: Solid laser optical axis 115: Brewster plate 130: Micro lens array 131: External mirror 140: Optical fiber

Claims

A semiconductor laser light source, and a solid-state laser medium that emits a pulsed laser light for fuel ignition when excited by a semiconductor laser light emitted from the semiconductor laser light source;
The solid-state laser medium is yttrium aluminum garnet (Nd: YAG) containing neodymium,
The semiconductor laser light source includes an array element in which vertical cavity surface emitting laser elements (VCSEL) in which a multilayer film is formed on both sides of an active layer are two-dimensionally arranged, and an oscillation center wavelength at 20 ° C. is 804. An on-vehicle ignition device characterized in that the temperature dependence of the oscillation center wavelength is 0.07 nm / ° C. or less.
2. The ignition device according to claim 1, wherein the solid-state laser medium is polycrystalline Nd: YAG containing 1.1 to 2.0 at% neodymium.
Polycrystalline yttrium aluminum garnet (Cr: YAG) containing chromium is joined to the end face of the solid laser medium,
Nd: YAG non-joint end face and Cr: YAG non-joint face are parallel,
Semiconductor laser light is incident on the non-joint end face of Nd: YAG,
3. The ignition device according to claim 1, wherein pulsed laser light is emitted from a non-bonding surface of Cr: YAG.
The ignition device according to claim 3, wherein a concave surface having a radius of 0.5 to 2 mm is formed on a non-bonding surface of Cr: YAG.
The optical fiber for guiding the semiconductor laser light emitted from the semiconductor laser light source to the solid laser medium is disposed between the semiconductor laser light source and the solid laser medium. The ignition device according to item.
A microlens array in which microlenses that individually collimate semiconductor laser light emitted from each light emitting point of the VCSEL are two-dimensionally arranged between the VCSEL and the Nd: YAG or between the VCSEL and the optical fiber; The ignition device according to any one of claims 1 to 5, wherein a mirror and microlens array in which a reflection film is integrally formed is disposed.
The VCSEL and a microlens array in which microlenses that individually collimate semiconductor laser light emitted from each light emitting point of the VCSEL are two-dimensionally arranged are fixed by an ultraviolet curable resin having a curing shrinkage rate of 2% or less. The ignition device according to any one of claims 1 to 6, wherein the ignition device is provided.
A semiconductor laser light source and a solid-state laser medium that emits pulsed laser light when excited by the semiconductor laser light emitted by the semiconductor laser light source;
The solid-state laser medium is yttrium aluminum garnet (Nd: YAG) containing neodymium,
The semiconductor laser light source includes an array element in which vertical cavity surface emitting laser elements (VCSEL) in which a multilayer film is formed on both sides of an active layer are two-dimensionally arranged, and an oscillation center wavelength at 20 ° C. is 804. A pulse laser beam emitting device characterized in that the temperature dependence of the oscillation center wavelength is 0.07 nm / ° C. or less, and 0.0 to 805.5 nm.