Surface emitting laser, information acquiring apparatus, imaging apparatus, laser array, and method of manufacturing surface emitting laser

A surface emitting laser having a wide wavelength tunable band is provided.A surface emitting laser includes a first reflecting mirror (102); a second reflecting mirror (116); and an active layer (104) arranged between the first reflecting mirror (102) and the second reflecting mirror (116), a gap being formed between the second reflecting mirror (116) and the active layer (104), an oscillation wavelength being tunable. The second reflecting mirror (116) includes a beam (108) comprising a single-crystal semiconductor, and a dielectric multilayer film (110) supported by the beam (108), and the dielectric multilayer film (110) is arranged in an opening (118) formed in the beam (108).

TECHNICAL FIELD

The present invention relates to a surface emitting laser, an information acquiring apparatus, an imaging apparatus, a laser array, and a method of manufacturing the surface emitting laser.

BACKGROUND ART

Since a wavelength tunable laser that can change its oscillation wavelength is expected to be applied to various fields, such as communication, sensing, and imaging, the wavelength tunable laser is being actively studied and developed in recent years. As such a wavelength tunable laser, a configuration that moves one of a pair of reflecting mirrors of a vertical cavity surface emitting laser (hereinafter, referred to as VCSEL) is developed. To be specific, the cavity length is varied by mechanically moving one (a movable mirror) of the pair of reflecting mirrors by micro electro mechanical systems (hereinafter, referred to as MEMS) technology and hence the oscillation wavelength of VCSEL is changed.

Also, for the movable mirror, a distributed Bragg reflector (hereinafter, referred to as DBR) may be used. NPL 1 discloses wavelength tunable VCSEL including dielectric DBR as a movable mirror.

CITATION LIST

Patent Literature

Non Patent Literature

SUMMARY OF INVENTION

Technical Problem

As shown in FIG. 4 of NPL 1, the dielectric DBR has a high reflectivity in a wide wavelength band. However, the reflectivity spectrum of the dielectric DBR has a region called dip in which the reflectivity is largely decreased as compared with other regions. In the wavelength tunable VCSEL, the oscillation threshold increases with the wavelength corresponding to the dip. Hence, oscillation hardly occurs, and the wavelength tunable band cannot be widened.

The present invention provides a surface emitting laser with a wide wavelength tunable band.

Solution to Problem

According to an aspect of the present invention, there is provided a surface emitting laser comprising a first reflecting mirror, a second reflecting mirror, and an active layer arranged between the first reflecting mirror and the second reflecting mirror, a gap being formed between the second reflecting mirror and the active layer, an oscillation wavelength being tunable. The second reflecting mirror includes a beam comprising a single-crystal semiconductor and a dielectric multilayer film supported by the beam, and the dielectric multilayer film is arranged in an opening formed in the beam.

According to another aspect of the present invention, there is provided a surface emitting laser comprising a first reflecting mirror, a second reflecting mirror, an active layer arranged between the first reflecting mirror and the second reflecting mirror, a gap being formed between the second reflecting mirror and the active layer. The second reflecting mirror includes a beam and a multilayer film supported by the beam, the multilayer film is arranged in an opening formed in the beam, and the multilayer film is arranged continuously from the opening to a portion around the opening of the surface of the beam opposite to the surface facing the active layer.

Also, according to another aspect of the present invention, there is provided a method of manufacturing a surface emitting laser, the surface emitting laser including a first reflecting mirror, a second reflecting mirror, and an active layer arranged between the first reflecting mirror and the second reflecting mirror, a gap being formed between the second reflecting mirror and the active layer, an oscillation wavelength being tunable. The method includes forming a first reflecting mirror, an active layer, and a sacrificial layer in that order; forming a beam precursor layer on the sacrificial layer, the beam precursor layer being made of a single-crystal semiconductor; forming an opening in the beam precursor layer, the opening penetrating through the beam precursor layer; forming a dielectric multilayer film in the opening; and removing the sacrificial layer, forming a gap between the second reflecting mirror and the active layer, and forming a beam.

Advantageous Effects of Invention

With the aspects of the present invention, the surface emitting laser with the wide wavelength tunable band can be obtained.

DESCRIPTION OF EMBODIMENTS

First, the above-described problems are described in detail.FIG. 8is a schematic cross-sectional view showing a surface emitting laser according to a comparative example. This surface emitting laser includes a first reflecting mirror502, an active layer504, a support layer506, and a second reflecting mirror516, arranged on a substrate500. The second reflecting mirror516includes a beam508, and a dielectric multilayer film (dielectric DBR)510formed on the beam508. A gap AG is formed between the second reflecting mirror516and the active layer504. Also, the beam508of the second reflecting mirror516is supported by the support layer506. A light emitting portion512is arranged in the active layer504. The light emitting portion512corresponds to the dielectric multilayer film510.

The beam508is made of a single-crystal semiconductor, and has electrical conductivity. The beam508vibrates in the thickness direction of the active layer504by applying alternating-current voltage between a first electrode524provided below the substrate500and a second electrode522provided above the beam508. Consequently, the dielectric multilayer film510also vibrates in the thickness direction of the active layer504, the cavity length of the pair of reflecting mirrors including the first reflecting mirror502and the second reflecting mirror516varies, and light with a specific wavelength corresponding to the cavity length among light emitted by the light emitting portion512is emitted to the outside. Thus, the oscillation wavelength of the surface emitting laser is tunable.

The reflection spectrum of the second reflecting mirror516according to the comparative example is indicated by a broken line inFIG. 2. As described above, a dip is present in the second reflecting mirror516according to the comparative example. The dip is a region in which the reflectivity is largely decreased by 0.5% or more as compared with other regions. To be specific, the reflectivity is largely decreased in a wavelength band from 1060 nm to 1095 nm. In such a region, it may be difficult to generate laser oscillation, and the wavelength tunable band may become small.

As the result that the inventors energetically repeated reviewing, it was found that this phenomenon occurred if the beam508was present below the dielectric multilayer film510. To be specific, an interference, in which reflected light R1reflected by a surface of the beam508at a side of the dielectric multilayer film510and reflected light R2reflected by a surface of the beam508at a side opposite to the dielectric multilayer film510weaken each other may occur with a specific wavelength according to the comparative example inFIG. 8.

To address this, a second reflecting mirror according to an embodiment of the present invention employs a configuration in which a beam has an opening and a dielectric multilayer film is arranged in the opening. With this configuration, since the beam is not provided at the position corresponding to a light emitting portion, the weakening interference in the beam does not occur. Consequently, as indicated by a solid line inFIG. 2, a dip is not generated in the reflection spectrum of the second reflecting mirror, and the wavelength tunable band can be widened.

A wavelength tunable surface emitting laser; and an information acquiring apparatus, an imaging apparatus, and a laser array including the surface emitting laser according to embodiments of the present invention are described below.

First Embodiment

FIG. 1is a schematic cross-sectional view showing an example of a surface emitting laser according to this embodiment. This surface emitting laser includes a first reflecting mirror102, an active layer104, a support layer106, and a second reflecting mirror116, arranged on a substrate100. The second reflecting mirror116includes a beam108, and a dielectric multilayer film (dielectric DBR)110supported by the beam108. A gap AG is formed between the second reflecting mirror116and the active layer104. Also, the beam108of the second reflecting mirror116is supported by the support layer106. A light emitting portion112is arranged in the active layer104. The light emitting portion112corresponds to the dielectric multilayer film110. It is to be noted that the substrate100, the first reflecting mirror102, the active layer104, and the support layer106may be occasionally collectively called semiconductor structure114.

The beam108is made of a single-crystal semiconductor, and has electrical conductivity. The beam108vibrates in the thickness direction of the active layer104by applying alternating-current voltage between a first electrode124provided below the substrate100and a second electrode122provided above the beam108. Consequently, the dielectric multilayer film110also vibrates in the thickness direction of the active layer104. The cavity length of the pair of reflecting mirrors including the first reflecting mirror102and the second reflecting mirror116varies, and light with a specific wavelength corresponding to the cavity length among light emitted by the light emitting portion112is emitted to the outside. Thus, the oscillation wavelength of the surface emitting laser is tunable.

Also, in the surface emitting laser according to this embodiment, the beam108has an opening118, and the dielectric multilayer film110is arranged in the opening118. The opening118is provided at a position corresponding to the light emitting portion112. Accordingly, as described above, the dielectric multilayer film110is also arranged at the position corresponding to the light emitting portion112. Consequently, the beam108is not arranged at the position corresponding to the light emitting portion112, and hence problems like those in the comparative example do not occur.

FIG. 2indicates the reflection spectrum of the second reflecting mirror116according to this embodiment with the solid line. It is to be noted that the broken line indicates the reflection spectrum of the second reflecting mirror516according to the comparative example inFIG. 8. As described above, it is found that this embodiment keeps high reflectivity in a wider wavelength band than that of the comparative example. Accordingly, the tunable wavelength band of oscillation wavelengths of the wavelength tunable surface emitting laser can be widened.

Also, with the configuration of the second reflecting mirror116according to this embodiment, the cavity length (the optical distance between the pair of reflecting mirrors) can be decreased as compared with the comparative example. To be specific, when n represents a refractive index of a beam made of a single-crystal semiconductor, and d represents a thickness of the beam, the cavity length according to this embodiment can be decreased by at least (n−1)×d as compared with the comparative example. If the cavity length is small, a longitudinal mode interval Δλ expressed in Expression 1 can be large. Accordingly, a mode hop unlikely occurs, and a stable wavelength sweeping operation can be provided. The expression is as follows:
Δλ=λ2/(2L)  Expression 1.

In this expression, λ represents a center wavelength of an oscillation wavelength band, and L represents a cavity length.

Also, a surface S1of the dielectric multilayer film110facing the active layer104protrudes from the opening118toward a side of the active layer104with respect to a surface S2of the beam108facing the active layer104. Accordingly, the cavity length can be further decreased. With this configuration, the mode hop can be further restricted.

Further, a surface S3of the dielectric multilayer film110opposite to the surface S1facing the active layer104may protrude from the opening118with respect to a surface S4of the beam108opposite to the surface S2facing the active layer104. Also, the surface S3and the surface S4may be at the same position, or the surface S3may be close to the active layer104with respect to the surface S4.

Also, the support layer106may have a configuration in which a plurality of support layers are stacked. In this case, the respective support layers are desirably made of different single-crystal semiconductors.

While the dielectric multilayer film110of the second reflecting mirror116uses the dielectric DBR, the combination forming a dielectric of a high refractive index and a low refractive index may be selected in accordance with the wavelength band to be used. For example, if the oscillation wavelength band of the surface emitting laser is a 1-μm band, the dielectric multilayer film110may use a multilayer film of Ta2O5and SiO2or a multilayer film of TiO2and SiO2. The reflection band as the dielectric multilayer film110is determined on the basis of the difference in refractive index between two dielectrics. Hence, it is important to have a large difference in refractive index between the two dielectrics as possible. On the other hand, the reflectivity of the dielectric multilayer film110increases if the number of stacked films increases. However, as the number of stacked films increases, the cost and difficulty in manufacturing increase. Also, a resonant frequency f of the second reflecting mirror116being a movable mirror is typically expressed by the following expression:
f=α×(k/m)1/2Expression 2.

In this expression, α represents a constant determined on the basis of the structure of the second reflecting mirror116, k represents a spring constant of the second reflecting mirror116, and m represents an effective mass of the second reflecting mirror116. As the number of stacked films of the dielectric multilayer film110increases, the mass increases, and hence the resonant frequency decreases as found from Expression 2. Owing to this, the number of stacked films of the dielectric multilayer film110is desirably as small as possible to be minimally required. For example, the number of stacked films is determined to attain a reflectivity of about 99.5% in a desirable wavelength band as one measure of the number of stacked films.

In the viewpoint of decreasing the mass of the second reflecting mirror116, the dielectric multilayer film110is desirably provided only in the opening118in the beam108corresponding to the light emitting portion112. On the other hand, in the viewpoint of durability of a dielectric multilayer film210, as shown inFIG. 3, the dielectric multilayer film210is desirably arranged continuously from the opening118in the beam108to a portion around the opening118of the surface S4of the beam108at the side opposite to the active layer104. With this configuration, the bonding area between the dielectric multilayer film210and the beam108can be increased, hence the adhesion between the dielectric multilayer film210and the beam108is increased, and peel-off of the dielectric multilayer film210from the beam108can be decreased.

Also, with the configuration shown inFIG. 3, it is desirable to decrease the thickness the portion of the beam108around the beam108as compared with the thickness of the remaining portion of the beam108other than the portion around the opening118. This can decrease occurrence of cutting the dielectric multilayer film210at a step of the opening118. For example, the thickness of the beam108may be continuously decreased toward the opening118as shown inFIG. 4A, or the thickness of the beam108may be decreased stepwise toward the opening118as shown inFIG. 4B.

Alternatively, the opening118may be formed in a through hole penetrating through the beam108as shown inFIG. 4C. Still alternatively, its plane shape may be circular, elliptic, or rectangular. Alternatively, the opening118may be a slit cutting the beam108as shown inFIG. 4D. That is, the beam108is not connected due to the opening118. In this case, as shown inFIG. 3, the dielectric multilayer film210is desirably arranged continuously from the opening118in the beam108to the portion of the beam108around the opening118.

The materials of respective layers of the semiconductor structure114may be selected in accordance with the wavelength to be used. For example, the respective layers of the semiconductor substrate114may use a GaAs-based material, an InP-based material, a GaN-based material, etc.

Also, the first reflecting mirror102may use dielectric DBR or semiconductor DBR. Also, the first reflecting mirror102may be a diffraction grating, for example, a high index contrast grating (hereinafter, referred to as HCG) mirror. The HCG mirror has a configuration in which a material with a high refractive index and a material with a low refractive index are alternately periodically arranged in the in-plane direction. For example, a configuration in which a high refractive region (Al0.7Ga0.3As) and a low refractive region (the air) are alternately periodically arranged in the in-plane direction can be obtained by partly removing a material with a high refractive index (for example, Al0.7Ga0.3As) and hence periodically forming a slit (an opening). As the HCG, one described in any of PTL 1 and PTL 2 can be used.

Also,FIG. 1illustrates an optical pumping surface emitting laser. Hence, an external light source (not shown) is provided as a unit configured to cause the surface emitting laser to emit light. However, the surface emitting laser according to this embodiment may be applied to an electrical pumping surface emitting laser. The electrical pumping surface emitting laser may additionally include a pair of electrodes for carrier injection. Alternatively, one of the first electrode124and second electrode122may also serve as one of the pair of electrodes for carrier injection. For example, a configuration may be employed in which a third electrode (not shown) is formed on the active layer104, the beam108is driven by applying alternating-current voltage between the second electrode122and the third electrode, current is applied to the light emitting portion112by using the first electrode124and the third electrode, and hence the light emitting portion112emits light. Also, the surface emitting laser according to this embodiment may have a defining structure that defines a light emitting region such as an oxidation confinement structure, or a current confinement structure that defines an electrical pumping region.

In this embodiment, the single surface emitting laser has been described. However, an embodiment of a laser array in which a plurality of surface emitting lasers are arranged in an array form may be applied.

Second Embodiment

In this embodiment, an example of an information acquiring apparatus using the surface emitting laser according to the first embodiment as a light source device is described. A wavelength tunable light source device can be used as a light source for optical communication or a light source for optical measurement. Further, a wavelength tunable light source device can be used as a light source device for an information acquiring apparatus that acquires information on the inside of a measurement object in a noninvasive and nondestructive manner. An optical coherence tomography apparatus (hereinafter, referred to as OCT apparatus) is described below with reference toFIG. 5, as an example of an information acquiring apparatus using a light source device according to this embodiment.

FIG. 5is a schematic illustration showing an OCT device8according to this embodiment. The OCT device8includes at least a light source device801, an interference optical system802, a light detecting unit803, and an information acquiring unit804that acquires information on the inside of a measurement object. The surface emitting laser according to the first embodiment or second embodiment may be used as the light source device801. Although not shown, the information acquiring unit804has a Fourier transformer. The configuration that the information acquiring unit804has the Fourier transformer is not particularly limited as long as the information acquiring unit804has a function of executing Fourier transform on input data. For example, the information acquiring unit804may have an arithmetic unit and the arithmetic unit may have the function of executing Fourier transform. To be specific, the arithmetic unit is a computer including CPU, and the computer executes an application having the Fourier transform function. For another example, the information acquiring unit804may have a Fourier transform circuit having the Fourier transform function.

Light output from the light source device801passes through the interference optical system802, and is output as interfering light having information on an object812of a measurement object. The interfering light is received by the light detecting unit803. The light detecting unit803may be a differential detecting type or a simple intensity monitoring type. Information on a time waveform of the intensity of the received interfering light is sent from the light detecting unit803to the information acquiring unit804. The information acquiring unit804acquires a peak value of the time waveform of the intensity of the received interfering light, executes Fourier transform, and hence acquires information (for example, information on a tomographic image) about the object812. The light source device801, the interference optical system802, the light detecting unit803, and the information acquiring unit804described above may be provided if desired.

A process from when light is emitted from the light source device801to when the information on the inside of the object being the measurement object is obtained is described in detail below. The light output from the light source device801passes through a fiber805, enters a coupler806, and is split into irradiation light passing through an irradiation-light fiber807and reference light passing through a reference-light fiber808. The coupler806is configured to operate in a single mode in the wavelength band of the light source. Various fiber couplers may be configured of 3-dB couplers. The irradiation light passes through a collimator809, hence becomes parallel light, and is reflected by a mirror810. The light reflected by the mirror810passes through a lens811, is emitted on the object812, and is reflected by respective layers in the depth direction of the object812.

On the other hand, the reference light passes through a collimator813, and is reflected by a mirror814. In the coupler806, interfering light is generated by the reflected light from the object812and the reflected light from the mirror814. The interfering light passes through a fiber815, passes through a collimator816to be collected, and is received by the light detecting unit803. Information on the intensity of the interfering light received by the light detecting unit803is converted into electric information such as a voltage and is sent to the information acquiring unit804. The information acquiring unit804processes the data of the intensity of the interfering light, or more particularly executes Fourier transform, and hence acquires information on a tomographic image. The data of the intensity of the interfering light for Fourier transform is data generally sampled at an interval of an equivalent number of waves. However, data sampled at an interval of an equivalent wavelength may be also used.

The acquired information on the tomographic image may be sent from the information acquiring unit804to an image display817and displayed as an image. By scanning the mirror810in a plane perpendicular to the incidence direction of the irradiation light, a three-dimensional tomographic image of the object812of the measurement object can be obtained. Also, the light source device801may be controlled by the information acquiring unit804through an electric circuit818. Although not shown, the intensity of light output from the light source device801may be continuously monitored and the data may be used for correcting the amplitude of the signal indicating the intensity of the interfering light.

An OCT device is suitable for acquiring a tomographic image of the inside of a living body, such as an animal or a human, in the fields of ophthalmology, dentistry, dermatology, etc. The information relating to a tomographic image of a living body includes not only a tomographic image of a living body but also numerical data required for acquiring a tomographic image. In particular, it is desirable to use an OCT device when a measurement object is an eye fundus, a tooth, or a blood vessel of a human body and information relating to a tomographic image of any of these is acquired.

This example relates to a surface emitting laser shown inFIG. 1. That is, the surface emitting laser is one corresponding to the first embodiment.FIGS. 6A to 6Eare illustrations explaining a method of manufacturing the surface emitting laser according to this example.

First, as shown inFIG. 6A, a first reflecting mirror102made of semiconductor DBR configured by stacking 30 pairs of AlAs/GaAs is formed on a GaAs substrate100. Then, an active layer104including a quantum well layer of InGaAs is formed on the first reflecting mirror102. Then, a GaAs sacrificial layer206and an (Al0.7Ga0.3)0.5As beam precursor layer208made of a single-crystal semiconductor are formed on the active layer104. The sacrificial layer206and the beam precursor layer208are formed respectively with thicknesses of 2120 nm and 909 nm. A portion of the sacrificial layer206becomes the support layer106inFIG. 1, and the beam precursor layer208becomes the beam108inFIG. 1. The beam precursor layer208is formed in a pattern that covers a region to be a light emitting portion of the active layer104and covers not the all of but only a portion of the sacrificial layer206. In this example, epitaxial growth is continuously provided from the first reflecting mirror102to the beam precursor layer208. Also, the beam precursor layer208is doped with Si by about 3×1018/cm3to increase electrical conductivity.

Then, as shown inFIG. 6B, an opening118is formed to penetrate through the beam precursor layer208. In this example, by using reactive ion etching (RIE) with SiCl4and Ar, overetching by 100 nm was executed on the beam precursor layer208, and hence the opening118extending to a portion of the sacrificial layer206was formed.

Then, as shown inFIG. 6C, a dielectric DBR layer120is formed on the beam precursor layer208and the sacrificial layer206through the opening118provided in the beam precursor layer208. In this example, the dielectric DBR layer is formed by stacking 8 pairs of TiO2/SiO2with an optical length of λ/4 by sputtering.

Then, as shown inFIG. 6D, the dielectric DBR layer120on the beam precursor layer208is removed by RIE using CF4, and hence a dielectric multilayer film110is formed only in the opening118.

Then, as shown inFIG. 6E, AuGe/Ni/Au are formed for a first electrode124, and Au/Ti are formed for a second electrode122. Further, a portion of the sacrificial layer206is selectively removed from the portion not covered with the beam precursor layer208by using an etchant containing citric acid and aqueous hydrogen peroxide, and hence a gap AG and a beam108are formed. A portion not removed among the sacrificial layer206serves as a support layer106. Thus, the surface emitting laser shown inFIG. 1is manufactured.

The solid line inFIG. 2illustrates the reflection spectrum of a second reflecting mirror116of the surface emitting laser manufactured as described above. Also, the broken line inFIG. 2illustrates the reflection spectrum of the comparative example shown inFIG. 8, that is, the second reflecting mirror516of the surface emitting laser without the opening118. As shown inFIG. 2, a dip with a large reflectivity is generated around 1082 nm in the comparative example, and a wavelength range with a reflectivity lower than 99.5% is generated for about 50 nm. In contrast, it can be recognized that the reflectivity of 99.5% is kept for 180 nm from about 970 nm to about 1150 nm in this example. That is, with this example, a wide wavelength tunable band can be ensured.

Also, the longitudinal mode interval was measured in the comparative example and this example. The longitudinal mode interval of the comparative example was 85 nm and the longitudinal mode interval of this example was 160 nm. Accordingly, a stable wavelength sweeping operation can be executed.

This example is for the surface emitting laser corresponding to the first embodiment.FIGS. 7A to 7Eare illustrations explaining a method of manufacturing the surface emitting laser according to this example. This example differs from Example 1 in that a plurality of sacrificial layers (a plurality of support layers) are provided. Other configurations are similar to those of Example 1. Points different from Example 1 are mainly described below.

First, as shown inFIGS. 7A to 7E, similarly to Example 1, a first reflecting mirror102and an active layer104are formed on a GaAs substrate100. Then, a GaAs first sacrificial layer306, an AlInP second sacrificial layer307, and an (Al0.7Ga0.3)0.5As beam precursor layer208made of a single-crystal semiconductor are formed on the active layer104. The first sacrificial layer306, the second sacrificial layer307, and the beam precursor layer208are formed respectively with thicknesses of 2120 nm, 100 nm, and 909 nm. Portions of the first sacrificial layer306and the second sacrificial layer307become support layers, and the beam precursor layer208becomes a beam. The beam precursor layer208is formed in a pattern that covers a region to be a light emitting portion of the active layer104and covers not the all of but only portions of the first sacrificial layer306and the second sacrificial layer307. Also in this example, similarly to Example 1, epitaxial growth is continuously provided from the first reflecting mirror102to the beam precursor layer208. Also, the beam precursor layer208is doped with Si by about 3×1018/cm3to increase electrical conductivity.

Then, as shown inFIG. 7B, an opening318is formed to penetrate through the beam precursor layer208. In this example, by using reactive ion etching (RIE) with SiCl4and Ar, overetching by 50 nm was executed on the beam precursor layer208. Then, wet etching was executed on the second sacrificial layer307by using a hydrochloricacid-based etchant, and hence an opening118was formed. The first sacrificial layer306was used as a stop layer in wet etching using the hydrochloric-acid-based etchant. In Example 1, when the opening318is formed, the depth of the opening318may vary for about 80 nm depending on the in-plane distribution of the etching speed of a RIE device. In this example, since the first sacrificial layer306is used as the etching stop layer, the variation in depth of the opening318can be decreased to about 10 nm.

The other part is similar to Example 1. That is, as shown inFIG. 7C, a dielectric DBR layer120is formed. Then, as shown inFIG. 7D, a portion of the dielectric DBR layer120arranged above the beam precursor layer208is removed, and a dielectric multilayer film110is formed only in the opening318. Then, as shown inFIG. 7E, a first electrode124and a second electrode122are formed. Further, a portion of the first sacrificial layer306and a portion of the second sacrificial layer307are selectively removed from the portion not covered with the beam precursor layer208. Thus, a gap AG and a beam108are formed. The remaining portions of the first sacrificial layer306and second sacrificial layer307not removed become a first support layer406and a second support layer407. Thus, a surface emitting laser is manufactured.

A second reflecting mirror116of the surface emitting laser in this example can obtain characteristics, in particular, the reflection spectrum and longitudinal mode interval, equivalent to the characteristics of the surface emitting laser in Example 1. In addition, although the surface emitting laser manufactured in Example 1 has a variation of about 12 nm in initial oscillation wavelength; however, the variation in this example is less than 2 nm. This is because a variation in depth of the opening318is decreased by using one of the plurality of sacrificial layers as the stop etching layer and hence a variation in initial cavity length can be decreased.

This application claims the benefit of Japanese Patent Application No. 2014-265572, filed Dec. 26, 2014 and No. 2015-222514 filed Nov. 12, 2015, which are hereby incorporated by reference herein in their entirety.

REFERENCE SIGNS LIST