WO2015136739A1 - 半導体レーザ装置 - Google Patents
半導体レーザ装置 Download PDFInfo
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- WO2015136739A1 WO2015136739A1 PCT/JP2014/073371 JP2014073371W WO2015136739A1 WO 2015136739 A1 WO2015136739 A1 WO 2015136739A1 JP 2014073371 W JP2014073371 W JP 2014073371W WO 2015136739 A1 WO2015136739 A1 WO 2015136739A1
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
- H01S5/3401—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers
- H01S5/3402—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers intersubband lasers, e.g. transitions within the conduction or valence bands
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/1092—Multi-wavelength lasing
- H01S5/1096—Multi-wavelength lasing in a single cavity
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/227—Buried mesa structure ; Striped active layer
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
- H01S5/3408—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers characterised by specially shaped wells, e.g. triangular
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
Definitions
- Embodiments described herein relate generally to a semiconductor laser device.
- Laser devices that emit infrared light are applied in a wide range of fields such as environmental measurement.
- the quantum cascade laser made of a semiconductor is small and highly convenient, and enables highly accurate measurement.
- the quantum cascade laser has, for example, GaInAs and AlInAs stacked alternately and has an active layer including a quantum well layer. Then, both side surfaces of the active layer have a structure sandwiched between, for example, InP clad layers.
- the cascade-connected quantum well layers can emit infrared laser light having a wavelength of 4 to 20 ⁇ m due to intersubband transition of carriers.
- a semiconductor laser device capable of emitting infrared light over a wide wavelength band.
- the semiconductor laser device of the embodiment includes a plurality of first unit stacks and a plurality of second unit stacks.
- the plurality of first unit stacked bodies include a light emitting region including a first quantum well layer and capable of emitting first infrared light by intersubband transition, and electrons relaxed to a miniband level in the light emitting region.
- the plurality of second unit stacks include a light emitting region including a second quantum well layer and capable of emitting second infrared light by intersubband transition, and a miniband in the light emitting region of the second quantum well layer.
- An electron injection region capable of transporting electrons relaxed to the level to the unit laminate on the downstream side.
- the second quantum well layer has at least one well width different from the well width of the first quantum well layer.
- the first unit stacked body and the second unit stacked body are stacked with a spatial periodicity.
- FIG. 1A is a schematic perspective view in which the semiconductor laser device according to the first embodiment of the present invention is partially cut
- FIG. 1B is a schematic cross-sectional view along the line AA.
- It is an energy band figure explaining the effect
- 4A is an energy band diagram of Example I of the second embodiment
- FIG. 4B is an enlarged view of the broken line region
- FIG. 4C is an energy band diagram of Example II
- FIG. 4 (e) is an energy band diagram of Example 3
- FIG. 4 (f) is an enlarged view of the broken line region.
- FIG. 6B is an enlarged view of the broken line region
- FIG. 6D is an enlarged view of the broken line region
- FIG. 6F is an enlarged view of the broken line region.
- FIG. 7A is a configuration diagram of the breath diagnosis apparatus using the semiconductor laser device according to the present embodiment
- FIG. 7B is a schematic diagram of absorption spectra of a plurality of gases
- FIG. 7C is a wavelength control unit. It is a figure explaining a 1st adjustment mechanism and a 2nd adjustment mechanism.
- FIG. 1A is a schematic perspective view in which the semiconductor laser device according to the first embodiment of the present invention is partially cut
- FIG. 1B is a schematic cross-sectional view along the line AA.
- the semiconductor laser device includes at least a substrate 10, a stacked body 20 provided on the substrate 10, and a dielectric layer 40.
- the first electrode 50, the second electrode 52, and the insulating film 42 are further provided.
- the stacked body 20 includes a first cladding layer 22, a first guide layer 23, an active layer 24, a second guide layer 25, and a second cladding layer 28.
- the refractive index of the first cladding layer 22 and the refractive index of the second cladding layer 28 are respectively lower than the refractive indexes of the first guide layer 23, the active layer 24, and the second guide layer 25,
- the infrared laser beam 60 is appropriately confined in the stacking direction of the active layer 24.
- the stacked body 20 has a stripe shape and can be called a ridge waveguide RG.
- the two end surfaces of the ridge waveguide RG are mirror surfaces, the stimulated emission light is emitted from the light exit surface as infrared laser light 62.
- the optical axis 62 is defined as a line connecting the centers of the cross sections of the optical resonator having the mirror surface as the resonance surface. That is, the optical axis 62 coincides with the extending direction of the ridge waveguide RG.
- the width WA in the direction parallel to the first surface 24a and the second surface 24b of the active layer 24 is too wide, a high-order mode is generated in the horizontal horizontal direction, It becomes difficult to obtain an output. If the width WA of the active layer 24 is set to 5 to 20 ⁇ m, for example, the control in the horizontal and transverse mode becomes easy. Assuming that the refractive index of the dielectric layer 40 is lower than the refractive index of any layer constituting the active layer 24, the dielectric layer 40 provided so as to sandwich the side surfaces 20a and 20b of the stacked body 20 causes the optical axis to be A ridge waveguide RG can be formed along the line 62.
- FIG. 2 is an energy band diagram for explaining the operation of the semiconductor laser device according to the first embodiment.
- the active layer 24 has a cascade structure in which light emitting regions and injection regions are alternately stacked.
- Such a semiconductor laser can be called a quantum cascade laser.
- the first unit stacked body 80 includes a first light emitting region 82 and a first injection region 84.
- the first injection region 84 includes an electron injection region 88 and an extraction barrier layer BE.
- the first injection region 84 can further include a tuning quantum well layer 90 on the downstream side.
- the first light emitting region 82 can emit the first infrared laser light by the intersubband transition of the first quantum well layer 86.
- Carriers are injected from the first injection region 84 into the second light emitting region 94, and electrons are extracted from the second light emitting region 94 to the second injection region 96 after the intersubband transition.
- the carrier moves from the upstream side to the downstream side. That is, the first unit stacked body 80 is located on the upstream side.
- the second unit laminated body 92 is located on the downstream side.
- the first injection region 84 transports (injects) carriers (electrons) to the second light emitting region 93 of the second unit stacked body 92 located on the downstream side.
- the second unit stacked body 92 has a second light emitting region 93 and a second injection region 95.
- the second injection region 95 includes an electron injection region 96 and an extraction barrier layer BE.
- the second injection region 95 can further include an adjustment quantum well layer 98 on the downstream side.
- the second light emitting region 93 can emit second infrared light including infrared laser light and the like by the intersubband transition of the second quantum well layer 94. Further, the second injection region 95 can relax the energy of carriers (electrons in this figure) injected from the second light emitting region 93 to the miniband level Lm2.
- the energy levels become discrete, and the subband (high level Lu) and subband (Low level Ll).
- Carriers such as electrons injected from the injection barrier layer BI can be effectively confined in the quantum well layer. For this reason, when the carrier transitions from the high level Lu to the low level Ll, light (hn) corresponding to the energy difference (Lu1-Ll1), (Lu2-Ll2), etc. is emitted (transition of carriers such as electrons) ).
- the intersubband transition occurs in either the conduction band or the valence band. That is, recombination of holes and electrons by a pn junction is not necessary, and light is emitted by transition of only one of the carriers.
- the semiconductor stacked body injects electrons 70 into the quantum well layer through the injection barrier layer BI by the voltage applied between the first electrode 50 and the second electrode 52, and the subband. Inter-transition occurs.
- the unit laminate has a plurality of minibands (also called subbands). It is preferable that the energy difference in the miniband is small and close to the continuous energy band.
- the electrons of the low level L11 in the first light emitting region 86 are relaxed to the miniband level Lm1, pass through the extraction barrier layer BE, are injected into the first injection region 88, and are transported to the unit laminate on the downstream side ( Injected). Further, the electrons of the low level L12 in the second light emitting region 93 are relaxed to the miniband level Lm2, pass through the extraction barrier layer BE, and are injected into the second injection region 95, to the unit laminate on the downstream side. Transported (injected).
- a well layer that determines intersubband transition is called a first well layer, and its width is represented by W1.
- the well layer width W1 that causes an electron transition accompanied by light emission in the second quantum well layer 94 is different from the well width W1 that causes an electron transition accompanied by light emission in the first quantum well layer 86.
- FIG. 3 is a graph of the gain with respect to the emission wavelength when the width of the first well layer is changed.
- the vertical axis represents the gain (1 / cm), and the horizontal axis represents the emission wavelength ( ⁇ m).
- the emission wavelength peak becomes , 6.1 ⁇ m, 6.15 ⁇ m, 6.2 ⁇ m, and 6.25 ⁇ m. Further, the peak of the emission wavelength can be changed by changing the width W1 of the first well layer of the unit laminate body.
- the first unit stacked body 80 and the second unit stacked body 92 are stacked with a spatial periodicity. For this reason, it is possible to obtain a quantum cascade laser having a plurality of unit laminated bodies having different widths W1 of the first well layers and having a wide emission wavelength band.
- first unit laminate 80 and the second unit laminate 92 can be alternately laminated.
- three or more kinds of unit laminates may be periodically laminated as ABCBCAB .... Further, it may be AABAAAB ....
- the number of stacked layers can be set to 20 to 50, for example.
- the substrate 10 may be InP or the like.
- the first cladding layer 22 and the second cladding layer 28 can be InP or the like.
- the first guide layer 23 and the second guide layer 25 may be InGaAs or the like.
- the active layer 24 may be InGaAs (In 0.53 Ga 0.47 As etc.) / In 0.52 Al 0.48 As etc.
- the first cladding layer 22 and the second cladding layer 28 have an n-type impurity concentration of, for example, 6 ⁇ 10 18 cm ⁇ 3 by Si doping, and can have a thickness of, for example, 1 ⁇ m. Further, the first guide layer 23 and the second guide layer 25 have an n-type impurity concentration of, for example, 4 ⁇ 10 16 cm ⁇ 3 and can have a thickness of 3.5 ⁇ m by Si doping. A part of the quantum well layer constituting the implantation region may be doped with Si.
- Table 1 is an example of a unit laminate structure constituting the quantum cascade laser according to the second embodiment.
- the adjustment quantum well layer 90 of the first unit stacked body 80 on the upstream side has a transition energy level Lt1 lower than the miniband level Lm1 adjacent to the downstream side and has a different emission wavelength.
- the second unit stacked body 92 is continuously generated up to the second quantum well layer 94.
- the width W1 of the first well layer is 6.3 nm, and no adjusted quantum well layer is provided.
- Example I (structure B + adjustment layer 1) of the second embodiment has an adjustment quantum well layer 90 consisting of one well layer / barrier layer pair.
- Example II has a tuned quantum well layer consisting of two well layers / barrier layer pairs (structure C + two well layers / barrier layer pairs).
- Example III has a tuned quantum well layer consisting of three well layers / barrier layer pairs (structure D + three well layers / barrier layer pairs).
- FIG. 4 (a) is an energy band diagram of Example I of the second embodiment
- FIG. 4 (b) is an enlarged view of the broken line region
- FIG. 4 (c) is an energy band diagram of Example II
- FIG. 4 (d) is an energy band diagram of Example II
- FIG. 4 (d) is an enlarged view of the broken line area
- FIG. 4E is an energy band diagram of Example 3
- FIG. 4F is an enlarged view of the broken line area.
- the adjusted quantum well layer 90 of the first unit stack 80 continuously generates the transition energy level Lt1 lower than the miniband level Lm1 up to the second light emitting region 94. . For this reason, even if the unit laminated body of a different structure is made into a cascade structure, electron injection efficiency can be kept high.
- FIG. 5 is a graph of the gain with respect to the emission wavelength of the semiconductor laser device according to the second embodiment.
- the implantation regions of Example I, Example II, and Example III of the second embodiment shown in (Table 1) are a pair of a well layer (thickness 2.5 nm) and a barrier layer (thickness 3 nm) having 1, 2, It has the adjustment quantum well layer 90 each laminated
- the electron injection efficiency can be increased, and the gain and light output can be increased. For this reason, it becomes easy to widen the emission wavelength band.
- the configuration of the adjusted quantum well layer 90 is not limited to these.
- the width of the well layer / barrier layer constituting the adjustment quantum well layer 90 and the repetition period can be determined.
- the cross section of the active layer 24 can be analyzed by TEM (Transmission Electron Microscope).
- FIG. 6B is an enlarged view of the broken line region
- FIG. 6D is an enlarged view of the broken line region
- FIG. 6F is an enlarged view of the broken line region.
- the comparative example is an energy band diagram of a unit laminate body in which no adjustment quantum well layer is provided.
- the unit stacked body 180 miniband level Lm1 is directly taken over by the quantum well layer 186 of the next unit stacked body (same configuration 180). It becomes the position Lu2. That is, there is no transition energy level lower than the miniband level Lm1 that facilitates electron injection near the interface. For this reason, the electron injection efficiency tends to decrease at the interface of the unit laminate body, and the light output decreases.
- At least two unit laminated bodies having different well layer widths are laminated while maintaining periodicity.
- a light emitting element including a quantum cascade laser capable of emitting infrared light in a wide wavelength band is provided.
- FIG. 7A is a configuration diagram of the breath diagnosis apparatus using the semiconductor laser device according to the present embodiment
- FIG. 7B is a schematic diagram of absorption spectra of a plurality of gases
- FIG. 7C is a wavelength control unit. It is a figure explaining a 1st adjustment mechanism and a 2nd adjustment mechanism.
- the breath diagnosis apparatus includes a quantum cascade laser 170 and the like, a wavelength control unit, a gas cell (corresponding to “casing”) 280, a detection unit 287, and a signal processing unit 288.
- the quantum cascade laser 170 and the wavelength control unit can be referred to as a light source unit 191.
- the wavelength control unit includes a first adjustment mechanism that shifts a wavelength of infrared laser light or the like into an absorption spectrum of one type of gas included in exhaled gas such as a human, and absorption of one type of gas. And a second adjustment mechanism that shifts in the spectrum.
- the first adjustment mechanism includes a diffraction grating 171 and the like.
- the diffraction grating 171 is provided so as to intersect the optical axis 162 of the quantum cascade laser 170 and constitutes an external resonator.
- FIG. 7 (c) in the breath BR containing a plurality of gases, the incident angle of the infrared laser light is changed to ⁇ 1 to ⁇ 4 or the like according to the absorption spectrum of each gas, and the wavelength of the infrared laser light is changed. (Coarse adjustment)
- the diffraction grating 171 is rotationally controlled around an axis that intersects the optical axis 162 by a stepping motor 199 and a controller 198 that controls the diffraction grating 171.
- a non-reflective coating film AR on the end face of the quantum cascade laser 70 on the diffraction grating 171 side.
- an external resonator can be formed with the diffraction grating 171.
- the molecular absorption spectrum is discrete and it is necessary to accurately match the wavelength to the absorption peak in order to improve measurement accuracy. Further, in order to avoid absorption of carbon dioxide and water, which are main components in exhalation, and to measure absorption of a molecule to be measured, it is necessary to accurately match the wavelength to the absorption peak. However, the absorption peak of the molecule and the wavelength of the light source may be affected and shifted due to the measurement environment. For this reason, it is preferable to perform fine adjustment using the second adjustment mechanism.
- the second adjustment mechanism keeps the diffraction grating 171 constant without rotating it.
- Wavelength adjustment is performed by changing the operating current value I LD or duty of the quantum cascade laser 170, changing the operating temperature of the quantum cascade laser 170 using the Peltier element 290, or changing the external resonator length by a piezo element or the like. It can be realized by, for example.
- the second adjustment mechanism may change the operating temperature of the quantum cascade laser 170 by any one or a combination of a chiller, a heater, and a refrigerant.
- the refrigerant can be, for example, liquid nitrogen, water, ethanol water, or liquid helium.
- the gas concentration of acetone (absorption peak on the vertical axis is near 7.37 ⁇ m) and methane (absorption peak is near 7.7 ⁇ m) is measured.
- the absorption spectra of different gases are largely separated from each other, for example, approximately 0.3 ⁇ m. For this reason, in order to measure a plurality of gases in a short time (for example, 1 minute), it is preferable to quickly increase the wavelength of the infrared laser light and increase the shift width by the first adjustment mechanism.
- the shift width when wavelength adjustment is performed within the absorption spectrum of one gas, the shift width may be narrower than the wavelength range in the first adjustment mechanism.
- it is required to increase the adjustment accuracy. That is, it is not easy to realize the first adjustment mechanism that is mainly coarse adjustment and the second adjustment mechanism that is mainly fine adjustment with the same wavelength control mechanism.
- the gas cell 280 has an exhalation inlet 281, an exhalation outlet 282, an infrared laser light incident window 283, and an infrared laser light exit window 284.
- the laser beam from the quantum cascade laser 170 has a divergence angle. Therefore, a collimating optical system 272 is preferably provided between the quantum cascade laser 170 and the incident window 283.
- a condensing optical system 286 may be provided between the exit window 284 and the detector 287.
- Human breath BR includes nitrogen, oxygen, carbon dioxide, water, etc. as main components. At the same time, 1000 or more kinds of different molecules are contained in a very small amount, and a change in a very small amount of gas becomes an indicator of a disease. For this reason, if the trace gas G1 contained in the exhalation is measured, it becomes possible to detect and prevent the disease early. By using the breath diagnosis apparatus in this way, it is possible to make a diagnosis in a short time and more easily than performing a blood test or the like.
- acetone can be detected as the trace gas G1
- diabetes can be found.
- a detection sensitivity of about ppm using infrared rays having a wavelength of 7 to 8 ⁇ m is required.
- hepatitis can be discovered if ammonia can be detected as a trace gas.
- detection sensitivity of about ppb is required using infrared rays having a wavelength of 10.3 ⁇ m. If ethanol or acetaldehyde can be detected as a trace gas, the amount of drinking can be measured.
- the emission wavelength band of the quantum cascade laser 170 is narrow, in order to generate infrared laser light in a wide wavelength range, a plurality of quantum cascade lasers 170, a plurality of external resonators corresponding to each quantum cascade laser, Is required. For this reason, an apparatus enlarges.
- the quantum cascade laser according to the present embodiment has a wide emission wavelength band. For this reason, infrared laser light having a wide range of wavelengths can be stimulated and emitted with one quantum cascade laser, and the device can be easily downsized.
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Abstract
Description
図1(a)は本発明の第1の実施形態にかかる半導体レーザ装置を部分切断した模式斜視図、図1(b)はA-A線に沿った模式断面図、である。
半導体レーザ装置は、基板10と、基板10の上に設けられた積層体20と、誘電体層40と、を少なくとも有する。図1(a)では、第1電極50と、第2電極52と、絶縁膜42と、をさらに有している。
活性層24は、発光領域と、注入領域と、が交互に積層されたカスケード構造を有する。このような半導体レーザを、量子カスケードレーザと呼ぶことができる。第1の単位積層体80は、第1発光領域82と、第1注入領域84と、有する。第1注入領域84は、電子注入領域88と、抽出障壁層BEと、を有する。また、第1注入領域84は、下流側に調整量子井戸層90をさらに有することができる。第1発光領域82は、第1量子井戸層86のサブバンド間遷移により、第1の赤外線レーザ光を放出可能である。第1注入領域84から第2発光領域94にキャリア(本図では電子)が注入され、サブバンド間遷移ののち、第2発光領域94から第2注入領域96に電子が引き抜かれる。キャリアは、上流側から下流側に移動する。すなわち、第1の単位積層体80は上流側に位置する。他方、第2の単位積層体92は下流側に位置する。たとえば、第1注入領域84は、キャリア(電子)を、下流側に位置する第2の単位積層体92の第2発光領域93に輸送(注入)すると言うことができる。
縦軸は利得(1/cm)、横軸は発光波長(μm)、である。
第1の井戸層の幅W1を、6.3nm(A)、6.4nm(B)、6.5nm(C)、6.6nm(D)と広くするのに応じて、発光波長のピークは、6.1μm、6.15μm、6.2μm、6.25μmと長くなる。また、単位積層体の第1の井戸層の幅W1を変えることにより、発光波長のピークを変えることができる。
例I、例II、例IIIにおいて、第1の単位積層体80の調整量子井戸層90は、ミニバンド準位Lm1よりも低い遷移エネルギー準位Lt1を第2発光領域94まで連続して生成する。このため、異なる構成の単位積層体をカスケード構造にしても電子注入効率を高く保つことができる。
(表1)に表す第2の実施形態の例I、例II、例IIIの注入領域は、井戸層(厚さ2.5nm)と障壁層(厚さ3nm)とのペアを1、2、3層とそれぞれ積層した調整量子井戸層90を有する。第2の実施形態では、電子注入効率を高める、利得や光出力を高めることができる。このため、発光波長帯域を広げることが容易となる。なお、調整量子井戸層90の構成はこれらに限定されない。キャリアの下流側にカスケード接続される発光領域の第1井戸層の幅W1に応じて、調整量子井戸層90を構成する井戸層/障壁層の幅や繰り返し周期を決めることができる。なお、活性層24の断面は、TEM(Transmission Electron Microscope)により分析可能である。
比較例は、調整量子井戸層が設けられない単位積層体のエネルギーバンド図である。W1=6.4、6.5、6.6μmのいずれにおいても、単位積層体180ミニバンド準位Lm1は、そのまま次の単位積層体(同じ構成180)の量子井戸層186に引き継がれ高準位Lu2となる。すなわち、界面近傍に電子注入を容易にするようなミニバンド準位Lm1よりも低い遷移エネルギー準位が存在しない。このため、単位積層体の界面で、電子注入効率が低下しやすく、光出力が低下する。
呼気診断装置は、量子カスケードレーザ170などと、波長制御部と、ガスセル(「筐体」に対応)280と、検出部287と、信号処理部288と、を有する。量子カスケードレーザ170と、波長制御部と、は、光源部191と呼ぶことができる。
Claims (12)
- 第1量子井戸層を含みサブバンド間遷移により第1の赤外光を放出可能な発光領域と、前記発光領域でミニバンド準位へ緩和された電子を下流側の単位積層体に輸送可能な電子注入領域と、を有する複数の第1の単位積層体と、
第2量子井戸層を含みサブバンド間遷移により第2の赤外光を放出可能な発光領域と、前記第2量子井戸層の前記発光領域でミニバンド準位へ緩和された電子を下流側の単位積層体に輸送可能な電子注入領域と、を有する複数の第2の単位積層体であって、前記第2量子井戸層は前記第1量子井戸層の井戸幅とは異なる井戸幅を少なくとも1つ有する、複数の第2の単位積層体と、
を備え、
第1の単位積層体と第2の単位積層体とは、空間的周期性を有して積層された半導体レーザ装置。 - 前記第1量子井戸層における前記サブバンド間遷移を決める井戸層の井戸幅は、前記第2量子井戸層における前記サブバンド間遷移を決める井戸層の井戸幅とは異なる請求項1記載の半導体レーザ装置。
- 前記複数の第1の単位積層体は、前記電子注入領域の下流側に調整量子井戸層を含み、
前記複数の第2の単位積層体は、前記電子注入領域の下流側に調整量子井戸層を含み、
第1の単位積層体と第2の単位積層体とが積層された界面において、上流側の単位積層体の調整量子井戸層は、上流側の電子注入領域のミニバンド準位よりも低い遷移エネルギー準位を、下流側に隣接する単位積層体の発光領域まで連続して生成する、請求項1記載の半導体レーザ装置。 - 前記複数の第1の単位積層体および前記複数の第2の単位積層体の少なくともいずれかの前記調整量子井戸層は、井戸層と障壁層とのペアを同一の構造で複数有する請求項3記載の半導体レーザ装置。
- 前記調整量子井戸層の上流側に隣接する電子注入領域は、複数の量子井戸層を含み、
前記調整量子井戸層の前記井戸層の幅および前記障壁層の幅は、前記複数の量子井戸層のうち隣接する量子井戸層を構成する井戸層の幅と障壁層の幅とそれぞれ同一である請求項4記載の半導体レーザ装置。 - 前記複数の第1の単位積層体は、前記第1量子井戸層に電子を注入する注入障壁層と、前記第1量子井戸層から電子を抽出する抽出障壁層と、を有し、
前記複数の第2の単位積層体は、前記第2量子井戸層に電子を注入する注入障壁層と、前記第2量子井戸層から電子を抽出する抽出障壁層と、を有する請求項1記載の半導体レーザ装置。 - 前記複数の第1の単位積層体は、前記電子注入領域の下流側に調整量子井戸層を含み、
前記複数の第2の単位積層体は、前記電子注入領域の下流側に調整量子井戸層を含み、
第1の単位積層体と第2の単位積層体とが積層された界面において、上流側の単位積層体の調整量子井戸層は、上流側の電子注入領域のミニバンド準位よりも低い遷移エネルギー準位を、下流側に隣接する単位積層体の発光領域まで連続して生成する、請求項2記載の半導体レーザ装置。 - 前記複数の第1の単位積層体および前記複数の第2の単位積層体の少なくともいずれかの前記調整量子井戸層は、井戸層と障壁層とのペアを同一の構造で複数有する請求項7記載の半導体レーザ装置。
- 前記調整量子井戸層の上流側に隣接する電子注入領域は、複数の量子井戸層を含み、
前記調整量子井戸層の前記井戸層の幅および前記障壁層の幅は、前記複数の量子井戸層のうち隣接する量子井戸層を構成する井戸層の幅と障壁層の幅とそれぞれ同一である請求項8記載の半導体レーザ装置。 - 第1量子井戸層を含みサブバンド間遷移により第1の赤外光を放出可能な発光領域と、前記発光領域でミニバンド準位へ緩和された電子を下流側の単位積層体へ輸送可能な電子注入領域と、を有する複数の第1の単位積層体と、
第2量子井戸層を含みサブバンド間遷移により第2の赤外光を放出可能な発光領域と、前記第2量子井戸層の前記発光領域でミニバンド準位へ緩和された電子を下流側の単位積層体へ輸送可能な電子注入領域と、を有する複数の第2の半導体積層体であって、前記第2量子井戸層は前記第1量子井戸層の井戸幅とは異なる井戸幅を少なくとも1つ有する、複数の第2の単位積層体と、
第3量子井戸層を含みサブバンド間遷移により第3の赤外光を放出可能な発光領域と、前記第3量子井戸層の前記発光領域でミニバンド準位へ緩和された電子を下流側の単位積層体へ輸送可能な電子注入領域と、を有する複数の第3の単位積層体であって、前記第3量子井戸層は前記第1量子井戸層の前記井戸幅および前記第2量子井戸層の前記井戸幅とは異なる井戸幅を少なくとも1つ有する、複数の第3の単位積層体と、
を備え、
第1の単位積層体と第2の単位積層体と前記第3の単位積層体とは、空間的周期性を有して積層された半導体レーザ装置。 - 前記第1量子井戸層における前記サブバンド間遷移を決める井戸層の井戸幅と、前記第2量子井戸層における前記サブバンド間遷移を決める井戸層の井戸幅と、前記第3量子井戸層における前記サブバンド間遷移を決める井戸層の井戸幅と、はすべて異なる請求項10記載の半導体レーザ装置。
- 前記複数の第1の単位積層体は、前記電子注入領域の下流側に調整量子井戸層を含み、
前記複数の第2の単位積層体は、前記電子注入領域の下流側に調整量子井戸層を含み、
前記複数の第3の単位積層体は、前記電子注入領域の下流側に調整量子井戸層を含み、
第1の単位積層体、第2の単位積層体、および第3の単位積層体のうちの2つが積層された界面において、上流側の単位積層体の調整量子井戸層は、上流側の電子注入領域のミニバンド準位よりも低い遷移エネルギー準位を、下流側に隣接する単位積層体の発光領域まで連続して生成する、請求項10記載の半導体レーザ装置。
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