WO2005078880A1 - 波長可変半導体レーザ及びそれを用いるガス検知装置 - Google Patents
波長可変半導体レーザ及びそれを用いるガス検知装置 Download PDFInfo
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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
- H01S5/10—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
- H01S5/12—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 the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
-
- 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
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
-
- 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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J3/42—Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry
- G01J3/433—Modulation spectrometry; Derivative spectrometry
-
- 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
- H01S5/02—Structural details or components not essential to laser action
- H01S5/024—Arrangements for thermal management
- H01S5/02407—Active cooling, e.g. the laser temperature is controlled by a thermo-electric cooler or water cooling
- H01S5/02415—Active cooling, e.g. the laser temperature is controlled by a thermo-electric cooler or water cooling by using a thermo-electric cooler [TEC], e.g. Peltier element
-
- 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
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
-
- 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
- H01S5/1039—Details on the cavity length
Definitions
- the present invention relates to a tunable semiconductor laser and a gas detection device using the same, and more particularly, to a tunable semiconductor laser in which the wavelength of emitted laser light is tunable, and a gas incorporating the tunable semiconductor laser. It relates to a detection device. Background art
- Gases such as methane, carbon dioxide, acetylene, and ammonia are known to absorb light of a specific wavelength in response to rotation of molecules, vibration between constituent atoms, and the like.
- Patent Document 1 A gas detection device using this light absorption characteristic is disclosed in Patent Document 1 below, for example.
- Patent Document 1 JP-A-11-326199
- a laser beam emitted from a semiconductor laser module in which a semiconductor laser is incorporated is transmitted through a gas to be measured made of, for example, methane or the like. Incident on the receiver.
- the semiconductor laser incorporated in the semiconductor laser module is a tunable semiconductor laser whose oscillation wavelength ⁇ changes according to the applied drive current I, as shown in the wavelength characteristic C of FIG. 10B.
- the oscillation wavelength ⁇ changes, and as shown in the intensity characteristic ⁇ of FIG. 10A, the laser emitted in response to the applied drive current I The light intensity X of light a also changes.
- the laser drive control unit adjusts the center current value I (bias current value) to half.
- the oscillation wavelength of the semiconductor laser is a value corresponding to the center wavelength.
- the wavelength ⁇ is changed from the semiconductor laser module around the absorption center wavelength ⁇ .
- the laser light that is wavelength-modulated around the absorption center wavelength ⁇ transmits the gas to be measured.
- the light After being absorbed in accordance with the absorption characteristic ⁇ during the transmission process, the light is received by a light receiver, converted into an electric signal, and input to the gas detector.
- the electric signal has a frequency component on the order of the modulation frequency.
- the conventional gas detection device as described above has the following problems to be solved yet.
- this gas detection device is often used for detecting gas leaks at the actual gas pipe piping construction site, used for periodic inspections after laying pipes, and used for detecting abnormalities in chemical factories.
- bias current value I current value
- frequency modulation efficiency 7 the degree of change in the oscillation wavelength (frequency) when the drive current I is changed by a unit current. Is very low, eg, less than 0.1 GHzZmA.
- the light intensity X of the laser beam a emitted from the semiconductor laser is not completely proportional to the current value I of the modulation signal b applied to the semiconductor laser. Near the upper limit of I, it tends to be saturated.
- Patent Document 2 US Pat. No. 6,351,479 Although Patent Document 2 discloses a semiconductor laser capable of obtaining high luminous efficiency and high output, the above-mentioned non-linear state of the intensity characteristic B increases. Analysis and improvement and frequency modulation efficiency improvement That's what you're thinking about.
- an object of the present invention is to provide a bias current value of a modulation signal to be applied to obtain a laser beam whose wavelength changes with an amplitude determined by an absorption characteristic around an absorption center wavelength. Can be set low, and the current amplitude of the modulation signal can be set small.As a result, power consumption can be suppressed.In addition, the nonlinear distortion of the intensity characteristic B can be improved to reduce the modulation distortion of the laser beam.
- An object of the present invention is to provide a wavelength tunable semiconductor laser capable of greatly improving the measurement accuracy of gas detection and a gas detection device incorporating the wavelength tunable semiconductor laser.
- a wavelength tunable semiconductor laser that can oscillate at the specific wavelength by injecting a current into the active layer (17) and change the specific wavelength by changing the magnitude of the current ( 27)
- the element length indicating the length in the propagation direction of the light generated in the active layer (17) is about 200 ⁇ m to 500 ⁇ m
- the p-type cladding layer (22) includes a low-concentration cladding layer (19) having a low impurity concentration and a high-concentration cladding layer (20) having a high impurity concentration, which are arranged in order from the active layer (17) side.
- a wavelength tunable semiconductor laser is provided.
- the element length L indicates the length in the propagation direction of light generated in the active layer (17). 00 is set to / im.
- the temperature change is small.
- the frequency indicating the degree of the wavelength change with respect to the applied current is reduced. Modulation efficiency is low.
- the area of the electrode to which a current is applied and the area of the active layer are reduced, so that the amount of current per unit area increases and the wavelength tunable.
- the temperature of the active layer of the type semiconductor laser tends to increase.
- the temperature of the active layer easily changes, and the oscillation wavelength ⁇ changes.
- the frequency modulation efficiency that indicates the degree of wavelength change with respect to the applied current increases.
- the noise current of the modulation signal to be applied to obtain a laser beam whose wavelength changes with an amplitude determined by the absorption characteristic around the absorption center wavelength is used.
- the value can be set low, the current amplitude of the modulation signal can be set small, and power consumption can be reduced.
- the optimum element length L is about 200 ⁇ m to 500 ⁇ m. Proven.
- the experimental results shown in FIG. 4 were obtained by using a wavelength tunable semiconductor laser device having an active layer width of 2.2 ⁇ m .
- the p-type cladding layer (22) located above the active layer (17) includes a low-concentration cladding layer (19) and a high-concentration cladding layer (20) in this order.
- the detection accuracy of the gas detection device incorporating the tunable semiconductor laser can be improved.
- a wavelength tunable semiconductor laser that can oscillate at the specific wavelength by injecting a current into the active layer (17) and change the specific wavelength by changing the magnitude of the current ( 27)
- the width of the active layer (17), which is perpendicular to the direction of propagation of light generated in the active layer (17) and parallel to the n-type semiconductor substrate, is about 1 ⁇ m to 2 ⁇ m. ⁇ m,
- the p-type cladding layer (22) includes a low-concentration cladding layer (19) having a low impurity concentration and a high-concentration cladding layer (20) having a high impurity concentration, which are arranged in order from the active layer (17) side.
- a wavelength tunable semiconductor laser is provided.
- the active layer width W indicating the length in the direction orthogonal to the propagation direction of the generated light in the active layer (17) is: It is set to about 1 ⁇ m to 2 ⁇ m.
- the width W of the active layer similarly to the above-described element length L, the narrower the active layer width W is, the smaller the active layer width W is.
- the width W of the active layer is optimally about 1 ⁇ m to 2 ⁇ m.
- the tunable semiconductor laser according to the second aspect of the present invention can exhibit substantially the same effects as the tunable semiconductor laser according to the first aspect of the present invention.
- a wavelength tunable semiconductor laser that can oscillate at the specific wavelength by injecting a current into the active layer (17) and change the specific wavelength by changing the magnitude of the current ( 27)
- the element length indicating the length of the light generated in the active layer (17) in the propagation direction is about 200 ⁇ 111 to 500111, and
- the width of the active layer (17), which is perpendicular to the direction of propagation of the light generated in the active layer (17) and parallel to the n-type semiconductor substrate (11), is about 1 ⁇ m.
- the p-type cladding layer (22) includes a low-concentration cladding layer (19) having a low impurity concentration and a high-concentration cladding layer (20) having a high impurity concentration, which are arranged in order from the active layer (17) side.
- a wavelength tunable semiconductor laser is provided.
- the element length L indicating the length of the light generated in the active layer (17) in the propagation direction is about 200 zm to about 200 zm.
- the width W of the active layer (17) is set to about 1 ⁇ m to 2 ⁇ m while being set to 500 ⁇ m.
- the wavelength tunable semiconductor laser according to the third embodiment can exhibit the same operation and effect as those of the wavelength tunable semiconductor lasers according to the first and second embodiments.
- a semiconductor laser module (la) incorporating a tunable semiconductor laser that emits laser light having a wavelength modulated at a predetermined frequency
- a gas detection device comprising: a gas detection unit that detects a gas to be measured based on an electric signal output from the light receiver (4); and (6),
- the tunable semiconductor laser incorporated in the semiconductor laser module (la) includes an n-type semiconductor substrate (11);
- a wavelength-tunable semiconductor laser that can oscillate at the specific wavelength by injecting a current into the active layer (17) and change the specific wavelength by changing the magnitude of the current ( 27)
- the element length indicating the length in the propagation direction of the light generated in the active layer (17) is about 200. / 1 111 to 500/1 111,
- the p-type cladding layer (22) includes a low-concentration cladding layer (19) having a low impurity concentration and a high-concentration cladding layer (20) having a high impurity concentration, which are arranged in order from the active layer (17) side.
- a gas detection device comprising:
- a semiconductor laser module (la) incorporating a tunable semiconductor laser that emits laser light having a wavelength modulated at a predetermined frequency
- the tunable semiconductor laser incorporated in the semiconductor laser module (la) includes an n-type semiconductor substrate (11);
- a wavelength tunable semiconductor laser that can oscillate at the specific wavelength by injecting a current into the active layer (17) and change the specific wavelength by changing the magnitude of the current ( 27)
- the width of the active layer (17), which is perpendicular to the direction of propagation of light generated in the active layer (17) and parallel to the n-type semiconductor substrate (11), is about 1 ⁇ m. m to 2 ⁇ m,
- the p-type cladding layer (22) includes a low-concentration cladding layer (19) having a low impurity concentration and a high-concentration cladding layer (20) having a high impurity concentration, which are arranged in order from the active layer (17) side.
- a gas detection device comprising:
- a semiconductor laser module (la) incorporating a tunable semiconductor laser that emits laser light having a wavelength modulated at a predetermined frequency
- a gas detection device comprising: a gas detection unit that detects a gas to be measured based on an electric signal output from the light receiver (4); and (5),
- the tunable semiconductor laser incorporated in the semiconductor laser module (1A) includes an n-type semiconductor substrate (11);
- a wavelength tunable semiconductor laser that can oscillate at the specific wavelength by injecting a current into the active layer (17) and change the specific wavelength by changing the magnitude of the current ( 27)
- the element length indicating the length in the propagation direction of the light generated in the active layer (17) ranges from about 200/1 111 to 500/1 111,
- the width of the active layer (17), which is perpendicular to the direction of propagation of the light generated in the active layer (17) and parallel to the n-type semiconductor substrate (11), is about 1 ⁇ m. ⁇ 2 ⁇ m,
- the p-type cladding layer (22) includes a low-concentration cladding layer (19) having a low impurity concentration and a high-concentration cladding layer (20) having a high impurity concentration, which are arranged in order from the active layer (17) side.
- a gas detection device comprising:
- the wavelength tunable semiconductor laser configured as described above
- a gas detection device incorporating the wavelength tunable semiconductor laser a laser beam whose wavelength changes with an amplitude determined by an absorption characteristic around an absorption center wavelength is obtained. Therefore, the bias current value of the modulation signal to be applied can be set low, and the current amplitude of the modulation signal can be set small, resulting in power consumption.
- the modulation distortion of the emitted laser beam can be reduced by improving the nonlinear state of the intensity characteristic B, and the measurement accuracy of gas detection for the gas to be measured can be greatly improved.
- the impurity concentration of the low-concentration cladding layer (19) is undoped or 3%.
- the impurity concentration of the high-concentration cladding layer (20) is about IX 10 18 / cm 3, while the impurity concentration is about X 10 17 / cm 3 .
- the concentration of the high-concentration cladding layer (20) is 8 ⁇ 10 17 Zcm 3 or more at the peak value, and preferably, the low-concentration cladding layer (20) is The concentration of the layer (19) is preferably undoped or 4 ⁇ 10 17 Zcm 3 or less and has a thickness of about 30 nm to 70 nm.
- the p-type cladding layer (22) is a medium-concentration cladding layer having a medium impurity concentration arranged subsequent to the high-concentration cladding layer (20). (21) is preferably further included.
- the p-type cladding layer (22) when Zn is a p-type impurity, has an impurity concentration of 5 ⁇ 10 It is preferably about 17 / cm 3 .
- a lower SCH (Separate Confinement Heteros corture: light) formed above the n-type semiconductor substrate (11) via a spacer layer (10).
- the structure of the tunable semiconductor laser (27) is changed.
- DFB distributed feedback type
- DR distributed reflection type
- DBR distributed Bragg reflector type
- PC partial diffraction grating type
- EC external resonance type
- FIG. 1 is a diagram showing a tunable semiconductor laser according to a first embodiment of the present invention cut along a light propagation direction.
- FIG. 2 is a cross-sectional view showing a cross section taken along line II-II of FIG. 1.
- FIG. 3 is a view showing an impurity concentration distribution in a p-type cladding layer in the wavelength tunable semiconductor laser according to the first embodiment of the present invention.
- FIG. 4 is a diagram showing the relationship between the element length L and the frequency modulation efficiency 77 in the wavelength tunable semiconductor laser according to the first embodiment of the present invention.
- FIG. 5 is a diagram showing a relationship between an active layer width W and a frequency modulation efficiency 77 in the wavelength tunable semiconductor laser according to the first embodiment of the present invention.
- FIG. 6A is a diagram showing characteristics of a conventional semiconductor laser.
- FIG. 6B is a diagram showing an example of characteristics of the wavelength tunable semiconductor laser according to the first embodiment of the present invention.
- FIG. 6C is a diagram showing another example of the characteristics of the tunable semiconductor laser according to the first embodiment of the present invention.
- FIG. 7 is a schematic diagram showing a schematic configuration of a gas detection device according to a second embodiment of the present invention.
- FIG. 8 is a diagram showing a schematic configuration of a semiconductor laser module and a laser drive control unit incorporated in a gas detection device according to a second embodiment of the present invention.
- FIG. 9 is a diagram showing a relationship between an absorption characteristic of a gas to be measured and a modulation signal according to a conventional gas detection device.
- FIG. 10A is a diagram showing light intensity characteristics of a semiconductor laser incorporated in a conventional gas detection device.
- FIG. 10B is a diagram showing oscillation wavelength characteristics of a semiconductor laser incorporated in a conventional gas detection device.
- FIG. 11 is a connection diagram shown to explain the tunable characteristic (Tunability) of the tunable semiconductor laser according to the first embodiment of the present invention.
- FIG. 12 is a waveform diagram of a heterodyne beat signal shown for explaining the tunable characteristics (Tunability) of the tunable semiconductor laser according to the first embodiment of the present invention.
- FIG. 1 is a cross-sectional view of a tunable semiconductor laser according to a first embodiment of the present invention, cut along a light propagation direction.
- FIG. 2 is a cross-sectional view of the tunable semiconductor laser of FIG. 1 taken along the line II-II.
- the tunable semiconductor laser 27 of the first embodiment is a distributed feedback type (Distributed
- FB Feedback: FB formed by a semiconductor laser.
- the diffraction grating layer 12 made of n- type InGaAsP is formed on the upper surface of the n- type semiconductor substrate 11 made of n-type InP. .
- the diffraction grating layer 12 is composed of a wavelength selecting means 15 having a plurality of gratings 13 and a plurality of gaps 14 existing between the plurality of gratings 13.
- the gap 14 is filled with the spacer layer 10, which also has an n-type InP force.
- n-type semiconductor substrate 11 Above the n-type semiconductor substrate 11, a lower SCH made of InGaAsP having an appropriate composition is used.
- a p-type cladding layer 22 made of p-type InP is formed on the upper surface of the upper SCH layer 18.
- the p-type cladding layer 22 includes a low-concentration cladding layer 19 having a low impurity concentration and a high-concentration cladding layer 20 having a high impurity concentration from the upper SCH layer 18 side.
- the high-concentration cladding layer 20 blocks carriers from the active layer 17 and simultaneously
- the concentration cladding layer 19 prevents Zn as an impurity from diffusing into the active layer 17.
- the concentration of the high-concentration cladding layer 20 has a peak value of 8 ⁇ 10 17 / cm
- the thickness of the low-concentration cladding layer 19 is made thinner than 30 nm, when Zn is used as an impurity, it diffuses to the active layer 17 and deteriorates the light emission characteristics. On the other hand, it becomes thicker than 70 nm. This is because carriers accumulate in the low-concentration cladding layer 19 and the effect of the carrier block cannot be obtained.
- the high-concentration cladding layer 20 since the function of the high-concentration cladding layer 20 is a block of carriers overflowing from the active layer 17, the high-concentration cladding layer 20 generally covers the entire cladding layer having a thickness of several ⁇ m. If necessary, the upper side of the high-concentration cladding layer 20 may be formed as a medium-concentration cladding layer 21 having an intermediate concentration between low concentration and high concentration.
- the peak value can be 7 ⁇ 10 17 / cm 3 or more even if the concentration is reduced by diffusion.
- the concentration of the middle concentration cladding layer 21 is preferably 5 ⁇ 10 17 / cm 3 to 7 ⁇ 10 17 / cm 3
- a lightly doped p-type cladding layer 19 and a heavily doped p-type cladding layer 19 are sequentially arranged from the upper SCH layer 18 side.
- a structure having a layer 20 and a moderately doped p-type cladding layer 21 will be described.
- FIG. 3 is a diagram showing an impurity concentration distribution in which Zn in the p-type cladding layer 22 is a p-type impurity.
- the impurity concentration of the low concentration cladding layer 19 is undoped or about 3 ⁇ 10 17 Zcm 3
- the impurity concentration of the high concentration cladding layer 20 is about 1 ⁇ 10 18 Zcm 3
- the impurity concentration distribution in which Zn in the p-type cladding layer 22 shown in FIG. 3 is a p-type impurity is also disclosed in the above-mentioned Patent Document 2 (US Pat. No. 6,351,479) by the present inventors. As described later, the analysis of the increase in the nonlinear state of the intensity characteristic B, which is an important subject of the present invention, and its improvement, and the improvement of the frequency modulation efficiency are discussed below. Ttere, nare,
- the impurity concentration of middle concentration cladding layer 21 is about 5 ⁇ 10 17 Zcm 3 .
- a p-electrode 23 is attached to the upper surface of the p-type cladding layer 22 via a contact layer (not shown) made of p-type InGaAs, and an n-electrode 24 is attached to the lower surface of the n-type semiconductor substrate 11. ing
- the element length L of the wavelength tunable semiconductor laser 27 in the light propagation direction is 300 Pm.
- the upper part of the n-type semiconductor substrate 11, the diffraction grating layer 12, the lower SCH layer 16, the active layer 17, the upper SCH layer 18, and a part of the p-type cladding layer 22 It is formed in a mesa shape.
- a p-type carrier layer 25 made of p-type InP and an n-type carrier layer 26 made of n-type InP are formed from below.
- the active layer 1 in the direction orthogonal to the light propagation direction of the wavelength tunable semiconductor laser 27 is
- the active layer width W of 7 is set to 1.5 / im.
- the active layer 17 emits light having multiple wavelengths. Out of the light having this wavelength, a light having a single wavelength ⁇ determined by the period of the diffraction grating layer 12, the equivalent refractive index, and the temperature is selected. Output as a.
- FIG. 4 shows the same structure as the wavelength tunable semiconductor laser 27 of the first embodiment.
- the type of gas to be detected is methane as described above
- only the element length L is 250 zm ⁇ 10%, 3 00 ⁇ ⁇ 10%, 350 1 m ⁇ 10%, 600 ⁇ m ⁇ 10%
- FIG. 6 is a characteristic diagram showing a relationship between the element length L and the frequency modulation efficiency 77 when the above-described frequency modulation efficiency 11 of each semiconductor laser is measured.
- this wavelength tunable semiconductor laser 27 is used as a laser light source of a gas analyzer, the required frequency modulation efficiency is 0.1 from the power consumption and the like and the modulation distortion of the laser light.
- the optimum range of the element length L of the tunable semiconductor laser 27 is about 200 zm to 500 zm (particularly, about 250 ⁇ m to 450 ⁇ m).
- the element length L is set to be 600 xm or more.
- the element length L is set to about 200 ⁇ —500 ⁇ , which is shorter than that of the conventional semiconductor laser.
- a modulation efficiency of 77 can be ensured, and as described above, the wavelength ⁇ is
- the bias current value I of the modulation signal b to be applied can be set low, and the current
- the width I can be set small, and power consumption can be reduced.
- FIG. 5 shows the same structure as the wavelength tunable semiconductor laser 27 of the first embodiment.
- the type of the gas to be detected is methane as described above, only the active layer width W is 1. l / im ⁇ 10%, 1.7 ⁇ ⁇ 10%, 2.2 ⁇ ⁇ 10%
- FIG. 4 is a characteristic diagram showing a relationship between a layer width W and a frequency modulation efficiency ⁇ .
- the frequency modulation efficiency ⁇ needs to be 0.1 GHzZmA or more.
- the optimum range of the active layer width W of the wavelength tunable semiconductor laser 27 is about 1 ⁇ m to 2 ⁇ m.
- the layer width W is set to 2 ⁇ m or more.
- the active layer width W is set to about lzm—which is shorter than that of the conventional semiconductor laser, sufficient frequency modulation efficiency is obtained.
- ⁇ can be secured, and as described above, the wavelength ⁇ is measured around the absorption center wavelength ⁇ .
- the bias current value I of the modulation signal b can be set low, and the current amplitude I of the modulation signal b is reduced.
- 0 W can be set, and power consumption can be reduced.
- the P-type cladding layer 22 located above the active layer 17 is formed from the active layer 17 side with a low-concentration cladding having a low impurity concentration. It comprises a layer 19, a high-concentration cladding layer 20 having a high impurity concentration, and a medium-concentration cladding layer 21 having a medium impurity concentration for suppressing absorption of light by holes in the p-type cladding layer 22.
- the p-type cladding layer 22 is constituted by the plurality of layers 19, 20, and 21 having different impurity concentrations, as described above. While sufficiently blocking carriers overflowing from the active layer 17, the diffusion of the p-type dopant into the active layer 17 is prevented, and the light absorption in the p-type cladding layer 22 is minimized. High luminous efficiency and high output can be obtained.
- the wavelength tunable semiconductor laser 27 of the first embodiment since the nonlinear state of the intensity characteristic B shown in FIG. 10A is improved, it is possible to reduce the modulation distortion of the emitted laser light. .
- the medium-concentration cladding layer 21 is not necessarily provided. It is a thing without it.
- the gas detection device incorporating the tunable semiconductor laser 27 of the first embodiment is Position detection accuracy can be improved.
- FIGS. 6A, 6B, and 6C show the effect of shortening the element length L and the active width W of the tunable semiconductor laser 27 of the first embodiment, and the effect of the high-concentration cladding layer 20 on the p-type cladding layer 22.
- FIG. 9 is a diagram showing a comparison between the characteristics of the wavelength tunable semiconductor laser 27 of the first embodiment and the characteristics of a conventional semiconductor laser in order to explain the provided effects.
- FIG. 6A shows intensity characteristics B and wavelength characteristics C of a conventional semiconductor laser.
- FIG. 6B shows the wavelength of the tunable semiconductor laser 27 according to the first embodiment of the present invention in which the element length L is reduced to about 300 ⁇ m and the width W of the active layer 17 is reduced to about 1.5 ⁇ m.
- the intensity characteristics B and wavelength characteristics C of the tunable semiconductor laser are shown.
- Modulation signal b applied to this tunable semiconductor laser to obtain 10 and light intensity X
- the intensity characteristic B and the wavelength characteristic C of the tunable semiconductor laser 27 of the first embodiment shown in FIG. 6B the amplitude required for the emitted wavelength-modulated laser light a
- the amplitude I of signal b is significantly lower than the amplitude I of the conventional semiconductor laser shown in Figure 6A.
- FIG. 6C shows that the device length L of the wavelength tunable semiconductor laser 27 and the width W of the active layer 17 of the first embodiment of the present invention are reduced to 300 zm and 1. Characteristics B and wave characteristics of the wavelength-tunable semiconductor laser 27 with the high-concentration cladding layer 20
- the nonlinear state is greatly improved compared to the intensity characteristic B of the conventional semiconductor laser shown in Fig. 6A and the intensity characteristic B of the wavelength-tunable semiconductor laser shown in Fig. 6B.
- the modulation distortion of the emitted laser light a can be reduced. As a result, it is possible to improve the detection accuracy of the gas detection device in which the wavelength tunable semiconductor laser 27 is incorporated.
- FIG. 11 is a connection diagram shown to explain the tunable property (Tunability) of the tunable semiconductor laser 27 according to the first embodiment of the present invention.
- FIG. 12 is a waveform diagram of a heterodyne beat signal according to the heterodyne beat method shown for explaining the tunability (Tunability) of the tunable semiconductor laser 27 according to the first embodiment of the present invention.
- the tunable characteristic (Tunability) is obtained by a heterodyne beat method using a measuring apparatus configuration as shown in FIG.
- the laser diode LD1 as a test chip has a frequency of 10K biased at 50mA.
- the other laser diode LD2 for obtaining the probe light as the reference light is operated by DC, and the wavelength of the laser light is close to the wavelength of the modulated laser light of the laser diode LD1. ing.
- Each of the laser diodes LD1 and LD2 is mounted on a bonded SiC block, and is thermally controlled by a thermoelectric cooler.
- Each laser diode LD1 and L is mounted on a bonded SiC block, and is thermally controlled by a thermoelectric cooler.
- Both laser beams from D2 are focused and coupled via a 3dB coupler 101 and an optical isolator (not shown).
- the combined laser light is detected by an optical-electrical (O / E) converter 102, and its output signal is observed by a spectrum analyzer 103.
- O / E optical-electrical
- Fig. 12 shows the laser diode LD1 as a test chip, which has approximately 0
- the R (3) absorption line of methane has a full width at half maximum of about 3.4 GHz
- the laser diode LD1 as this test chip can change the wavelength over the FWHM of methane by modulating the power of 12mA.
- FWHM full width at half-maximum
- the method of measuring the wavelength tunability (Tunability) using the heterodyne beat method is the same as the method of measuring the wavelength tunable semiconductor laser 27 of the first embodiment of the present invention, The data that is most useful when used in a detector is obtained, and the characteristics of the tunable semiconductor laser 27 are compared.
- a laser diode LD (hereinafter, referred to as LD1) on the upper side of the figure is the wavelength tunable semiconductor laser 27 of the first embodiment of the present invention, and includes a laser diode and a modulation circuit as the test chip.
- the laser diode LD1 is modulated with an amplitude of 5 mA (10 mA) peak-to-peak, for example, centered at 50 mA, and the wavelength (optical frequency) of the light output from the laser diode LD1 is also corresponding to the modulation. Modulated.
- the lower laser diode LD (hereinafter, referred to as LD 2) in the drawing corresponds to the other laser diode LD 2 for obtaining the probe light as the above-described reference light.
- the laser diode LD2 Since the laser diode LD2 operates at DC, the light wavelength (optical frequency) is fixed, and the wavelength of light from the laser diode LD2 is close to that of the laser diode LD1 (LD1).
- the difference frequency between LD2 and LD2 is within the band of the O / E converter described later.
- the light from laser diode LD1 and the light from laser diode LD2 are multiplexed by 3-dB power blur 101, and the multiplexed light is received by ⁇ / E converter 102, and the frequency difference between the two is obtained.
- An electric signal (beat) having the following frequency is observed by the spectrum analyzer 103.
- the frequency difference between the light of the laser diode 1 and the light of the laser diode LD2 also changes according to the modulation, that is, the beat frequency also changes according to the modulation.
- the beat frequency changed by 3.4 GHz
- the laser diode LD the laser diode LD
- the frequency variable width of 1 can be estimated to be 3.4 GHz.
- Active layer width W l.7 zm, with an average of 0.6 GHz / mA. ing.
- the wavelength tunable characteristic of the wavelength tunable semiconductor laser 27 of the first embodiment is at least three to seven times the wavelength tunable characteristic of the conventional semiconductor laser. I understand that there is.
- FIG. 7 is a schematic diagram illustrating a schematic configuration of the gas detection device according to the second embodiment of the present invention.
- the tunable semiconductor laser 27 according to the first embodiment is incorporated in a semiconductor laser module la.
- the laser beam “a” emitted from the semiconductor laser module la in which the tunable semiconductor laser 27 is incorporated passes through the gas to be measured 3 made of, for example, methane or the like, and enters the light receiver 4.
- the measured gas 3 composed of methane has, for example, an absorption center wavelength shown in FIG.
- the laser drive control unit 2a sends out the modulation signal b to the tunable semiconductor laser 27 incorporated in the semiconductor laser module la.
- FIG. 8 is a diagram showing a schematic configuration of the semiconductor laser module la and the laser drive control unit 2a.
- the temperature of the tunable semiconductor laser 27 is controlled by the Peltier device 31.
- the laser light a emitted from one emission end of the tunable semiconductor laser 27 is output to the outside of the semiconductor laser module la via the focusing lens 29 and the protective glass 30.
- the laser light emitted from the other emission end of the wavelength tunable semiconductor laser 27 is After being converted into parallel light by a lens 32, the light is transmitted through a reference gas cell 33 filled with the same methane gas as the measured gas 3 as a reference gas, and is incident on a light receiver 34.
- the light receiver 34 converts the intensity of the incident laser light into an electric (current) signal and inputs the electric signal to the current / voltage converter 35 in the laser drive control unit 2a.
- the laser drive control unit 2a includes a current-voltage converter 35, a fundamental wave signal amplifier 36, a signal differentiation detector 37, a wavelength stabilization control circuit 38, a temperature stabilization PID circuit 39, a laser drive And a circuit 40.
- Current-voltage converter 35 converts the electric signal of light receiver 34 into a voltage.
- the fundamental wave signal amplifier 36 amplifies the voltage converted by the current-voltage converter 35.
- the signal differentiation detector 37 differentiates the voltage waveform amplified by the fundamental wave signal amplifier 36 to generate a shift signal of the absorption center wavelength ⁇ power of the reference gas.
- the wavelength stabilization control circuit 38 controls to stabilize the emission wavelength ⁇ of the tunable semiconductor laser 27 to the absorption center wavelength ⁇ of the reference gas.
- the wavelength stabilization control circuit 38 converts the shift signal from the signal differential detector 37 into the temperature of the wavelength-tunable semiconductor laser 27, outputs the temperature to the temperature stabilization PID circuit 39, and performs control based on the shift signal.
- the signal is output to the laser drive circuit 40.
- the temperature stabilization PID circuit 39 controls the Peltier element 31. That is, the temperature stabilization D circuit 39 performs PID control in accordance with the temperature signal from the wavelength stabilization control circuit 38 so that the wavelength of the wavelength tunable semiconductor laser 27 becomes a temperature at which the semiconductor laser 27 oscillates at a desired wavelength. The temperature of the laser 27 is stably maintained at a constant temperature.
- the laser drive circuit 40 is configured such that the current value I (bias current value) at the center is a tunable semiconductor.
- the oscillation wavelength ⁇ of the laser 27 is a value corresponding to the absorption center wavelength ⁇ of the absorption characteristic ⁇ ⁇ ⁇ of the reference gas (gas 3 to be measured) as shown in FIG.
- the voltage is applied to the tunable semiconductor laser 27 incorporated in a.
- the laser driving circuit 40 operates in accordance with the temperature signal from the wavelength stabilization control circuit 38.
- the cardiac current value I bias current value
- the laser beam emitted from the tunable semiconductor laser 27 is transmitted through the reference gas cell 33 in which the same methane gas as the gas 3 to be measured is sealed.
- the wavelength tunable semiconductor laser 2 is adjusted so that the center wavelength of the laser light matches the absorption center wavelength; I of the absorption characteristic A of the reference gas (gas 3 to be measured) as shown in FIG.
- the laser light a wavelength-modulated to 0 is absorbed according to the absorption characteristic A as shown in FIG. 9 in the process of passing through the gas 3 to be measured, and then received by the light receiver 4 to receive an electric (current) signal c. And is input to the gas detector 5. Since the light receiver 4 does not have the wavelength resolution of the laser light a, the electric (current) signal c has a frequency component on the order of the modulation frequency.
- the gas detector 5 includes a current-to-voltage converter 41, a fundamental signal detector 42, a second harmonic signal detector 43, and a divider 44.
- the current-voltage converter 41 converts the input electric (current) signal c into a voltage electric signal c and sends it to the fundamental signal detector 42 and the second harmonic signal detector 43.
- the divider 44 calculates the ratio (D / ⁇ ) between the amplitude D of the second harmonic signal d and the amplitude D of the fundamental signal d.
- the element length L is about 300 zm
- the active width W is about 300 zm. Reduced to about 1.
- the p-type cladding layer 22 The wavelength tunable semiconductor laser 27 provided with the cladding layer 20 is employed.
- this gas detection device can suppress power consumption in the semiconductor laser module la and the laser drive control unit 2a, and greatly suppress modulation distortion of the laser light a incident on the gas to be measured 3. Therefore, as described above, the measurement accuracy for the measured gas 3 is greatly improved.
- the present invention has been made with respect to a wavelength tunable semiconductor laser that simultaneously controls light output and oscillation wavelength with a single current, and a gas detection device using the same.
- specific semiconductor laser structures include distributed feedback (DFB), distributed reflection (DR), distributed Bragg reflector (DBR), partial diffraction grating (PC), and external resonance type.
- DFB distributed feedback
- DR distributed reflection
- DBR distributed Bragg reflector
- PC partial diffraction grating
- a force using only the InP substrate and a material that can be epitaxially grown thereon is not limited to these, and a GaN system, a GaAs system, or the like can also be used. is there.
- the present invention it is possible to set a low bias current value of a modulation signal to be applied to obtain a laser beam whose wavelength changes with an amplitude determined by an absorption characteristic around an absorption center wavelength, and The current amplitude of the modulation signal can be set small, resulting in reduced power consumption.
- the nonlinearity of the intensity characteristics can be improved to reduce the modulation distortion of the laser beam, and the measurement accuracy of gas detection for the gas to be measured can be greatly improved. It is possible to provide a wavelength tunable semiconductor laser that can be improved to a high degree, and a gas detection device incorporating the wavelength tunable semiconductor laser.
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP05710105A EP1717918A4 (en) | 2004-02-16 | 2005-02-10 | SEMICONDUCTOR LASER WITH VARIABLE WAVELENGTH AND GAS SENSOR THEREOF |
US10/548,394 US20060187976A1 (en) | 2004-02-16 | 2005-02-10 | Variable-wavelength semiconductor laser and gas sensor using same |
NO20054737A NO20054737L (no) | 2004-02-16 | 2005-10-14 | Halvlederlaser med variabel bolgelengde og gassfoler som benytter denne |
Applications Claiming Priority (2)
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JP2004037801A JP2005229011A (ja) | 2004-02-16 | 2004-02-16 | 波長可変半導体レーザ及びガス検知装置 |
JP2004-037801 | 2004-02-16 |
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WO2005078880A1 true WO2005078880A1 (ja) | 2005-08-25 |
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PCT/JP2005/002053 WO2005078880A1 (ja) | 2004-02-16 | 2005-02-10 | 波長可変半導体レーザ及びそれを用いるガス検知装置 |
Country Status (6)
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US (1) | US20060187976A1 (ja) |
EP (1) | EP1717918A4 (ja) |
JP (1) | JP2005229011A (ja) |
CN (1) | CN1765037A (ja) |
NO (1) | NO20054737L (ja) |
WO (1) | WO2005078880A1 (ja) |
Families Citing this family (16)
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WO2009119790A1 (ja) * | 2008-03-28 | 2009-10-01 | 株式会社堀場製作所 | 光分析計及び分析計用波長安定化レーザ装置 |
US7943915B2 (en) * | 2008-10-10 | 2011-05-17 | Ge Infrastructure Sensing, Inc. | Method of calibrating a wavelength-modulation spectroscopy apparatus |
US7957001B2 (en) * | 2008-10-10 | 2011-06-07 | Ge Infrastructure Sensing, Inc. | Wavelength-modulation spectroscopy method and apparatus |
WO2013016249A2 (en) * | 2011-07-22 | 2013-01-31 | Insight Photonic Solutions, Inc. | System and method of dynamic and adaptive creation of a wavelength-continuous and prescribed wavelength versus time sweep from a laser |
CN102368591B (zh) * | 2011-10-28 | 2013-04-24 | 武汉华工正源光子技术有限公司 | 一种条形掩埋分布反馈半导体激光器的制作方法 |
JP2013113664A (ja) * | 2011-11-28 | 2013-06-10 | Yokogawa Electric Corp | レーザガス分析装置 |
EP2610608B1 (en) * | 2011-12-27 | 2016-07-20 | HORIBA, Ltd. | Gas measurement apparatus and method for setting the width of wavelength modulation in a gas measurement apparatus |
JP5933972B2 (ja) * | 2011-12-27 | 2016-06-15 | 株式会社堀場製作所 | ガス計測装置およびガス計測装置における波長変調幅の設定方法。 |
JP6467166B2 (ja) * | 2014-08-19 | 2019-02-06 | 浜松ホトニクス株式会社 | 波長掃引型半導体レーザ素子及びガス濃度測定装置 |
EP3001180A1 (de) * | 2014-09-29 | 2016-03-30 | Siemens Aktiengesellschaft | Verfahren und Gasanalysator zur Messung der Konzentration einer Gaskomponente in einem Messgas |
CN104792730B (zh) * | 2015-04-17 | 2018-02-16 | 山东大学 | 一种基于光波导激光结构的血糖浓度探测器及其制备方法与应用 |
CN105406355B (zh) * | 2015-12-22 | 2018-06-29 | 中国科学院半导体研究所 | 共腔双波长分布反馈激光器的制作方法 |
EP3543682B1 (de) * | 2018-03-22 | 2020-04-29 | Axetris AG | Verfahren zum betreiben eines optischen messsystems zur messung der konzentration einer gaskomponente in einem messgas |
CN108776277B (zh) * | 2018-07-04 | 2020-10-09 | 歌尔股份有限公司 | 激光器检测装置以及方法 |
CN109802299A (zh) * | 2019-03-20 | 2019-05-24 | 青岛海信宽带多媒体技术有限公司 | 一种用于硅光子电路的高功率分布反馈布拉格光栅激光器 |
EP3799231B9 (en) * | 2019-09-27 | 2024-04-24 | ams International AG | Optical device, photonic detector, and method of manufacturing an optical device |
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- 2005-02-10 CN CN200580000140.8A patent/CN1765037A/zh active Pending
- 2005-02-10 WO PCT/JP2005/002053 patent/WO2005078880A1/ja not_active Application Discontinuation
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Also Published As
Publication number | Publication date |
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JP2005229011A (ja) | 2005-08-25 |
CN1765037A (zh) | 2006-04-26 |
EP1717918A1 (en) | 2006-11-02 |
NO20054737D0 (no) | 2005-10-14 |
US20060187976A1 (en) | 2006-08-24 |
NO20054737L (no) | 2006-06-07 |
EP1717918A4 (en) | 2007-05-16 |
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