EP0495874A1 - Appareil permettant de stabiliser la longueur d'onde d'un faisceau lumineux module par signal - Google Patents

Appareil permettant de stabiliser la longueur d'onde d'un faisceau lumineux module par signal

Info

Publication number
EP0495874A1
EP0495874A1 EP19900915543 EP90915543A EP0495874A1 EP 0495874 A1 EP0495874 A1 EP 0495874A1 EP 19900915543 EP19900915543 EP 19900915543 EP 90915543 A EP90915543 A EP 90915543A EP 0495874 A1 EP0495874 A1 EP 0495874A1
Authority
EP
European Patent Office
Prior art keywords
wavelength
laser
signal
light beam
atomic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19900915543
Other languages
German (de)
English (en)
Inventor
Hans Göran Evald Martin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0495874A1 publication Critical patent/EP0495874A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • H01S5/0687—Stabilising the frequency of the laser
    • 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
    • H01S5/06837—Stabilising otherwise than by an applied electric field or current, e.g. by controlling the temperature

Definitions

  • the invention presented here refers to a device or an apparatus for making possible a wavelength or frequency stabilization of a semiconductor laser, where its laser beam in a known manner is modulated by a signal, and where said beam, with superimposed signal, is sensed by a photoreceiver.
  • semiconductor lasers are comparatively inexpensive to purchase but also that they generate an emission, whose wavelength, or light frequency, changes with pressure, temperature and other circumstances, in the range of several percents.
  • TITUTE SHEET In any case, it is very difficult from one occation or application to another, with different external conditions, to make such a semiconductor laser generate one and the same light beam with a fixed wavelength.
  • gas lasers for their operation are based on a discharge, which is, as by nature, inhomogenous and, consequently, gives some variations in frequency and wavelength.
  • a variable optical distance of the laser cavity is therefore used to adjust for proper fine wavelength.
  • the regulation is usually accomplished by mechanical adjustments, that is the distance between the mirrors is controlled mechanically.
  • SUBSTITUTE SHEET It must also be considered a technical task to create conditions at different times of use so that a semiconductor laser directly will emit one particular wavelength, corresponding to one out of several available atomic transitions, for instance those of oxygen, and to lock and regulate the emitted wavelength towards this selected fixed wavelength.
  • the beam of a semiconductor laser arranged for wavelength stabilization by using its own photosignal, contains information about at least one atomic transition in the medium where the light beam passes and when several such fixed wavelengths corresponding to different atomic transitions can not be excluded for one and the same medium such as air, it has to be considered a technical problem that for the adjustment of one fundamental wavelength among several possible atomic transitions to realize that the temperature for this laser has to be selected within a narrow temperature region and the current through the semiconductor laser has to be adjusted within a narrow region, which in practise means that every semiconductor laser used has to be precalibrated such that the wavelength of the emitted laser beam is determined as a function of temperature and laser current.
  • SUBSTITUTE SHEET It also has to be considered a technical consideration, including a qualified technical problem, that for measuring a concentration of a gas in a medium, transmitted by the laser beam, using a semiconductor laser, one only need to evaluate the value of the amplitude in the photodetector, receiving said laser beam with the fixed wavelength, where this value of the amplitude is comparable with the amplitude value of another signal for the same wavelength acting as a calibration of the same atomic transition in a well defined known concentration.
  • the present invention starts by offering a device or an apparatus making possible a wavelength stabilization of a semiconductor laser where its laser beam is modulated by a signal, for instance 2 kHz, whereafter said signal is sensed by a photo-receiver.
  • the ciriuitry should be arranged in such a way that it can sense the atomic transitions in the medium where the light beam propagates.
  • the laser is attributed parameters (temperature, current, etc.) that are adjustable so that the laser emits a light beam with a wavelength corresponding to, or dominantly corresponding to, the wavelength of one selected atomic transition.
  • a regulation circuitry is arranged such that if the emitted light beam deviates from the wavelength of the atomic transition it will generate error signals for the attributed laser parameters such that the wavelength is forced towards the fixed wavelength selected.
  • the necessary wavelength region for a capturing range must be chosen depending on which fixed wavelength is chosen, taking into account necessary information regarding other nearby located optical resonances.
  • said regulation circuitry should be arranged in such a way that
  • the regulation circuitry is arranged such that it affects the semiconductor injection current and/or semiconductor laser temperature such that every tendency of wavelength change will be compensated for by an appropriate variation in the laser current and/or actual temperature.
  • said modulating signal should be the subject of an adjustment in order to offer a well defined regulation region, or capturing region, resulting in a pronounced negative and a pronounced positive feedback signal value, respectively, on each side of said fixed chosen wavelength.
  • the modulation signal amplitude is variable so that with an increased value the defined capturing range increases, particularly during a start up sequence, whereafter the amplitude of the signal should be continuously decreased from this high level down to a normal level, in order to approach a well defined narrow regulation region.
  • the temperature of the laser is chosen to a value which at a predetermined laser current will make the laser emit at a wavelength which in any case will be close to the wavelength of said chosen atomic transition.
  • a method is proposed, using a wavelength stabilized semiconductor laser of the sort described above, of measuring the concentration of a gas in a beam propagating medium, where the value of this concentration is evaluated from the value of the received light intensity at a chosen fixed wavelength. This is trivial in the case where another signal is calibrated for the same atomic transition at a certain established concentration.
  • This measure of the gas concentration is made by a sequential measurement.
  • a somewhat more complex device to establish the momentary value of a gas concentration uses two laser beams in a parallel measurement, one wavelength stabilized beam in a reference cell containing a know gas concentration and one
  • BSTITUTE SHEET beam through the concentration of gas to be evaluated. In this way it is possible to evaluate the unknown concentration using a continuous calibration.
  • Another possibility is to have the semiconductor laser locked to an atomic transition in a gas, for instance oxygen, and having another beam from the same laser passing through a solution, in which the momentary concentration (of oxygen) can be evaluated.
  • a gas for instance oxygen
  • the invention also offers the possibility of measuring a fluid concentration by parallel measurements by simply determining the amplitude of one of the photo- signals, when the amplitude value of another signal is calibrated for the same atomic transition in a certain established concentration in the same fluid.
  • the emitted wavelength should be locked to a chosen atomic transition for a gas found in air.
  • a device for achieving an extremely good wavelength stabilization, a device is proposed where the light from one wavelength-locked laser, modulated around an atomic transition as already discussed, is interacting with that of a second non-modulated laser, having the same centre wavelength as the first one, thereby producing a heterodyne signal on a second fast response photo-receiver, which is used to produce an error signal for the centre wavelength of said second non- modulated laser, which then indirectly becomes locked to said atomic transition.
  • the benefits linked to a device are the creation of possibilities of, by simple means, using a semiconductor laser and making its wavelength stable at a wavelength determined by an atomic transition in a gas, present in the beam propagating medium, and making the semiconductor laser lock at said wavelength at any time, by choosing a proper capturing range and regulation region selected in such a way that the laser wavelength will not lock onto an adjacent atomic transition, and consequently a "wrong" wavelength.
  • Figure 1 shows, in a very simplified scheme, the principles of a device for making possible a wavelength stabilization of the light beam emitted by a semiconductor laser, to a chosen fixed wavelength determined by an atomic transition,
  • Figure 2 shows a circuit for automatic sensitivity adjustment and automatic gain control, connected to a photo-receiver
  • Figure 3a shows the transmittance properties of the earth's atmosphere at low spectral resolution as a function of wavelength of light propagating perpendicular to the surface of the earth
  • Figure 3b shows a part of Figure 3a magnified, in the region of oxygen absorption, around 0.76 pm wavelength
  • Figure 3c shows a part of Figure 3b magnified, showing oxygen absorption wavelengths at high resolution
  • Figure 4a shows a signal obtained from an analogue electro-optic derivation of the wavelength dependent signal in figure 3c, suitable for regulation of the semiconductor laser towards a fixed wavelength " ⁇ L ",
  • Figure 4b shows how the wavelength dependent signal in Figure 4a is changed when the applied modulation amplitude is increased compared to the case in Figure 4a
  • Figure 5 shows a normalized detector signal suitable for wavelength stabilization without the need to modulate the laser
  • Figure 6 shows a device for wavelength stabilizing a semiconductor laser for the purpose of using it for measuring the concentration of gas in an unknown sample, relative to a known reference sample, to which by absorption the wavelength of the laser is locked, where the dotted parts of the Figure are meant to illustrate a possible way for a continuous correction of possible time
  • SUBSTITUTE SHEET varying optical losses, using a second laser, not shown in the figure, having a wavelength differing from any atomic absorption wavelength
  • Figure 7 shows a device where one semiconductor laser is stabilized in accordance with the principles of the invention, and a second laser is made, by heterodyne technique in addition to the principles of the present invention, to emit the same central wavelength as the first one, but without any modulation superimposed.
  • a device is shown, using a block diagram, for making possible a frequency, or wavelength, stabilization of a beam 2, emitted by a semiconductor laser 1, where said beam is modulated by a LF-signal generated by the electronics 3.
  • This modulation can vary and is here chosen to 2 kHz.
  • the light beam 2 passes the medium “M” and is sensed in a photo-receiver 4, which by a wire 5 is connected to an automatic sensitivity adjustment and an automatic gain control 6, with its block diagram, shown in Figure 2.
  • Figure 1 shows that the circuit 6 is connected by a wire 8 ' with a phase sensitive amplifier 8, arranged for demodulating the electronic signals from circuit 6 and, as a result, generating a regulating signal to the semiconductor laser 1 so that this will increase or decrease the wavelength of the emitted beam 2.
  • This regulating signal is consequently arranged for affecting the semiconductor laser 1 such that it is automatically wavelength stabilized towards a fixed wavelength.
  • a temperature regulator 7 keeps the laser at a certain temperature.
  • the temperature regulation can be accomplished using a photo- receiver, monitoring the laser intensity - too high intensity when the wavelength is locked means an increase in the temperature, and vice versa.
  • a photo-receiver 4 setup is shown with an automatic sensitivity adjustment 6a, a buffer amplifier 6b, and an automatic gain control 6c. Since these different parts are previously known as such, no detailed schematics are given on these subjects.
  • the electronics 6c is connected to the amplifier and demodulator circuit 8, using the wire 8'.
  • the upper photo signal 10 illustrates the constant amplitude, controlled by the electronics 6, and shows two significant absorption dips 10a and 10b, due to one atomic resonance transition.
  • the signal is conditioned by the electronics 8, by familiar synchronous or rectifying technique, which in this case will generate a positive error signal, which will regulate the operating parameters for the semiconductor laser 1 to increase its emitting wavelength.
  • the middle signal 11 indicates that absorption dips 11a and lib occur in such a way that the electronics 8 will, in this case, generate a negative error signal with a decreasing wavelength change as a result.
  • the lower signal function 12 indicates an error free situation at a fix chosen wavelength, in which case the absorption dips 12a and 12b are in the correct symmetric sequence.
  • FIG 3a the transmittance properties of the earth's atmosphere are shown at low spectral resolution for light propagating perpendicular towards the earth's surface.
  • the graph represents the wavelength dependent intensity variation seen by the photo-receiver 4 when a laser beam 2 propagates through the air.
  • wavelength stabilization in accordance with the present invention, one can here choose one, among a large number of distinct absorption dips, since they all represent atomic transitions.
  • the wavelength dependent photo signal 13 representing the absorption spectrum at high resolution, shows a pronounced signal dip 13a, which in this example has been chosen to be the fix wavelength standard " ⁇ L ".
  • This dip 13a has a line width of about 0.000006 ⁇ m at atmospheric pressure and is symmetrical around the fix wavelength " ⁇ L ".
  • SUBSTITUTE SHEET Of importance, for the invention, is to know the appearence of adjacent signal dips 13b and the magnitude of the wavelength difference 13d. With this knowledge, it is possible to make the regulation electronics selective enough to guarantee that the wavelength cannot be locked onto the "wrong" signal dip 13b.
  • a current deviation of about 15 mA may also cause the risk of trapping the wavelength in the wrong dip 13b.
  • the electronics can be made to regulate the wavelength towards the predetermined fix wavelength.
  • Figure 4a shows the centre wavelength dependent error signal, for the situation shown in Figure 3c, caused by the electro-optic derivation obtained from the laser wavelength modulation.
  • the signal demodulation and low pass filtering take place in the electronics 8, making the signal 4a suitable for regulating the semiconductor laser towards the fix wavelength " ⁇ L ".
  • the signal 14 shows a positive region 14a and a negative region 14b, which together form the "capturing" range "A" in between.
  • the magnitude of the capture range "A" depends on the amplitude of the modulating signal and, consequently, can be reduced towards the lower limit, which equals the oxygen linewidth.
  • E SHEET An alternative to the startup sequence just described, is to give the predetermined laser operation parameters starting values that produce a startup wavelength that is on the "safe", in this case, long wavelength side of " ⁇ L ".
  • a constant low offset, added to the regulating error signal, will in this " example tend to reduce the laser wavelength until it reaches the capture range "A” and, consequently, lock on " ⁇ L " without the risk of locking to the "wrong” dip 13b.
  • the semiconductor laser used will have to be calibrated, or so investigated, that one knows at what temperature and what laser current, or other indirect measures of these quantities, a certain emission wavelength occurs, so that a good choice of these operational parameters can be made, in order to force the laser towards a certain chosen wavelength.
  • the electronic principle shown in Figure 2 solves the problem of making the following signal processing independent of time, in spite of time dependent factors, like dirt accumulation, dealignment of the optics, vibrations and other possible disturbances. Furthermore, it offers a possibility for subtraction the pure AM component in the photo-receiver signal, the "carrier wave", by using, for instance, the common laser diode internal emission intensity monitor in a duplicate amplifier scheme, thereby making it possible to amplify the pure effect of atomic transitions to a larger extent, than otherwise possible, especially in cases when this absorption is very weak compared to the pure amplitude modulation.
  • a wavelength stabilized semiconductor laser is very well suited for a sequential measurement of actual gas concentration, simply by evaluating the recieved signal amplitude, in particular the analogue second derivative generated from the signal function 3c as the laser wavelength is modulated. For the purpose of calibration, it is convenient to take advantage of the amplitude value of a second signal, obtained for the same atomic transition but at a known concentration.
  • the medium “M” is natural air and the wavelength stabilization is made using a transition in oxygen, then the absorption amplitude 13a' of the signal 13a shown in Figure 3c, can be calibrated to 21,6% oxygen.
  • a wavelength stabilized semiconductor laser as described above, can also be used for measuring actual concentration in a fluid using a parallel measurement and simply evaluating the amplitude of a signal. Also here, it is suggested that, for the purpose of calibration, the amplitude of a second signal at a certain wavelength and a known concentration is used.
  • the present invention thus offers a possibility of wavelength stabilization, at the accuracy previously discussed, and is based on a feedback of the processed signal from an atomic/molecular transition.
  • a slight wavelength modulation of the laser in combination with phase sensitive detection of a wavelength dependent signal (i.e. laser absorption, laser induced emission, opto-galvanic effect, or any other laser spectroscopic method of detection), a derivation of the latter signal can be obtained (odd harmonics for regulation purposes), which after proper amplification can serve as the error signal for the regulation circuit.
  • a wavelength dependent signal i.e. laser absorption, laser induced emission, opto-galvanic effect, or any other laser spectroscopic method of detection
  • a derivation of the latter signal can be obtained (odd harmonics for regulation purposes), which after proper amplification can serve as the error signal for the regulation circuit.
  • the laser wavelength is locked to the central wavelength of the atomic transition.
  • the laser wavelength can be locked to said atomic reference, but in this case not to the central wavelength but to the slopes of the absorption line 13a. This is shown for the inverted signal in Figure 5.
  • This locking position is defined by a user set reference signal level (ref). If this dispersive signal by nature is stable in the amplitude, or otherwise is normalized in a proper manner with respect to the signal affecting factors, then this method of stabilization may also be good, giving a reproducible wavelength that is known or can be calibrated.
  • reference signal level ref
  • a combination of the proposed methods for wavelength stabilization can under some circumstances provide new advantages.
  • a non-modulated highly stable semiconductor laser can be locked with an even higher accuracy to a temperature stabilized long high-finesse interferometer, whose cavity modes are actively coupled to an atomic transition using, for instance, a second wavelength stabilized laser in the spirit of the present invention.
  • stabilized laser wavelengths can be realized that do not necessarily have to coincide with the atomic transition wavelengths available, but can differ from these by some multiple of the interferometer free spectral range.
  • a non-modulated laser with a stable long coherence length, can be locked to the centre wavelength of a modulating wavelength stabilized laser, discussed previously, through heterodyne technique, creating an even higher wavelength accuracy coupled to an atomic transition.
  • Oxygen (0.76 ⁇ m), water vapour (0.81 ⁇ m, 0.92 ⁇ m, 1.1 ⁇ m, 1.4 ⁇ m, 1.9 ⁇ m), and carbon dioxide (1.4 ⁇ m, 2.0 ⁇ m, 2.7 ⁇ m) are available everywhere at the surface of the earth without needing to include any extra gas cell in the device (the wavelengths in parantheses show some examples on spectral regions for these gases, where absorption wavelengths are found that can be used for the realization of present invention).
  • a reflexion of some percent of the laser beam from some external optical component may give information enough for the system to lock its wavelength at a pre-determined absorption line in the air.
  • the laser temperature can, for example, be regulated to a predetermined temperature chosen such that the resulting laser wavelength is approximately correct, good enough for the electronics to be within the capture range, or automatically drift towards the capture range, for the selected absorption line.
  • the laser modulation amplitude can during this startup sequence be enlarged, in order to temporarily increase the locking dynamics.
  • FIG. 6 describes a device in the spirit of the invention.
  • a low-cost commercially available GaAlAs-semiconductor laser 30 (Mitsubishi ML4405) emits a laser beam through a pathlength 31-32-33 to a photo-receiver 34.
  • the wavelength is in the 0.76 ⁇ m spectral region where oxygen has absorption lines with absorption strengths of the order of two percent per metre air. No other species than oxygen has significant absorptions in this chosen spectral region.
  • the laser 30 has an internal photo-receiver monitoring the intensity of the emitted laser radiation. If this tends to be too high, a transistor 38 lowers the regulation voltage to the laser current regulator 39, in order to prevent the laser intensity from increasing additionally.
  • the laser will partly be heated fast, by the laser current, and partly slowly, by the resistive heating 40.
  • Heating results in an increase of the laser wavelength.
  • the laser is wavelength modulated by the oscillator 34, through a small modulation of the laser current.
  • phase sensitive (odd harmonics, preferably three times the modulation frequency) demodulator 36 output is biased by a constant offset in adder 37.
  • This offset is high enough to make the laser regulator 39 drive the laser as high as to execute the laser light limit function.
  • the only event that can make the light level decrease, and the transistor 38 open up the ground connection, is that a spectral absorption line will be scanned through as the laser wavelength is increased.
  • the amplified negative going signal of the demodulator output 36 will affect the laser regulator 39 so that the laser intensity will decrease and, consequently, the transistor 38 will disconnect the ground.
  • the driving of the laser has now turned from a light regulated mode into a current regulated mode, regulated by the derivative signal of the spectral absorption line, that is a wavelength stabilized situation.
  • the laser wavelength is trapped to that of the atomic transition.
  • the light limiting signal that affects the transistor 38 also affects the transistor 41, which in turn regulates the laser ambient temperature through the resistive heating 40. In this way, the heating of the laser will stop once the laser wavelength have been trapped by an atomic absorption, and the long term stabilization will be assured through this temperature regulation, which keeps the laser intensity at a level that optimizes the dynamics of the wavelength capture range by fast laser current regulation.
  • the device just described can be expanded to give a measure of the concentration of the molecules/atoms to which transition the laser wavelength is locked.
  • Let the pathlength 31-32-33 constitute a reference cell containing said gas at a known concentration.
  • Let an equally long pathlength 31-42-43 constitute a measuring cell containing a sample gas with an unknown concentration of the reference medium to be determined.
  • the first harmonic overtone (or any even multiple of this) of the laser modulation frequency, resulting in symmetric line profiles with maximum amplitudes at the stabilized wavelength.
  • the signal-to-noise ratio of the absorption signal is generally better for the harmonics than for the fundamental frequency, because of possible noise in the amplitude modulation.
  • the selected overtone is filtered by the demodulator circuits 44 and 45.
  • a differential amplifier 46 will make the detection more sensitive and reduce unwanted effects of noise in the laser in addition to supressing the pure laser amplitude modulation (the carrier wave).
  • An analogue divider 47 finally computes in real time the percentage deviation between the two concentrations in the form (A-B)/A which is presented on the display 48.
  • SUBSTITUTE SHEET pathlengths with the light from another laser that is not in resonance with any atoms or molecules in the gases.
  • This laser is modulated at another frequency 53, different from that of the wavelength stabilized laser, and also illuminates the photo-receivers 33 and 43.
  • the influence of the pure optical losses in the system, measured using this second laser wavelength can be traced in the parallel electronics and used to normalize the gas measuring signals according to the formula (A1-B1)/A1 ⁇ A2/(A2-B2).
  • the value of the wavelength is of no importance at all. Consequently, the laser is allowed to lock at the first absorption line found for the correct gas.
  • the previously described startup sequence will have to be used, in order to assure one and the same known laser wavelength in every situation, irrespective of different environmental conditions.
  • a reset signal should automatically provide for a new startup sequence with a new automatic search for said transition.
  • the modulation amplitude shall be decreased to a small value comparable to the value of the spectral linewidth, or even smaller, in cases when wavelength accuracy is of great importance.
  • This facility is easily accomplished, for instance, using a semi-grounded transistor connected to the centre leads of a voltage divider, scaling down the modulation amplitude with a time constant given by a RC network connected to the base of said transistor.
  • Figure 7 shows an apparatus where one semiconductor laser 1 is stabilized according to the principles of the invention, and this is made to interact with a second laser 1 ' by heterodyne technique, for the purpose of making a long term wavelength stabilized laser beam at a known wavelength and without any modulation superimposed, that is a beam with a very long coherence length.
  • the beat frequency of the optical wave 22 is registered by the fast photo-receiver 4', and processed by the wide bandwidth electronics 6', which generates the necessary error signal to regulate the laser 1 ' to emit a wavelength of beam 2' that equals the central atomic wavelength, without any modulation of beam 2'.

Landscapes

  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Semiconductor Lasers (AREA)

Abstract

l'invention concerne un appareil permettant la stabilisation d'une longueur d'onde d'un faisceau lumineux émis (2) généré par un laser à semiconducteur (1) et modulé par un signal (3). Ledit faisceau (2) est détecté par un photorécepteur (4), l'électronique étant connectée audit photorécepteur de sorte qu'une longueur d'onde fixe représentant une transition atomatique selectionnée dans le milieu (M) où se propage ledit faisceau est détectée. Les paramètres fonctionnels (température, courant etc.) du laser (1) sont réglables de sorte que l'émission laser (2) ait une longueur d'onde correspondant, essentiellement, à une longueur d'onde fixe déterminée d'une transition automatique du milieu (M) selectionnée. Un circuit de réglage (8) est conçu de manière à générer les paramètres de signal nécessaires pour que longueur d'onde de tout faisceau lumineux émis (2), dont la déviation de la longueur d'onde fixe est déterminée par la transition atomique, soit réglée à ladite longueur d'onde fixe. Une zone de longueur d'onde pour une étendue de capture est selectionnée en fonction de la longueur d'onde fixe choisie.
EP19900915543 1989-10-13 1990-10-02 Appareil permettant de stabiliser la longueur d'onde d'un faisceau lumineux module par signal Withdrawn EP0495874A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8903363 1989-10-13
SE8903363A SE463952B (sv) 1989-10-13 1989-10-13 Anordning foer att moejliggoera en vaaglaengdsstabilisering av en av en halvledarlaser alstrad och utsaend ljusstraale

Publications (1)

Publication Number Publication Date
EP0495874A1 true EP0495874A1 (fr) 1992-07-29

Family

ID=20377123

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900915543 Withdrawn EP0495874A1 (fr) 1989-10-13 1990-10-02 Appareil permettant de stabiliser la longueur d'onde d'un faisceau lumineux module par signal

Country Status (5)

Country Link
EP (1) EP0495874A1 (fr)
AU (1) AU6547090A (fr)
FI (1) FI921592A0 (fr)
SE (1) SE463952B (fr)
WO (1) WO1991006141A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2256308B (en) * 1991-05-29 1995-04-19 Northern Telecom Ltd Binary modulation of injection lasers
SE9201921L (sv) * 1992-06-23 1993-12-24 Hans Martin Som en gas- och/eller vätskesensor tjänande ljusvågledare samt anordning för att från en central enhet övervaka och/ eller påverka en, av ett flertal, perifer enhet, lämpligen utnyttjande en sådan ljusvågledare
FI20105476A (fi) 2010-04-30 2011-10-31 Vaisala Oyj Ilmakehän kosteus- tai lämpötilaprofiilin tai pilvenkorkeuden mittausmenetelmä ja -laitteisto
US11916350B2 (en) * 2022-04-24 2024-02-27 ColdQuanta, Inc. Multi-quantum-reference laser frequency stabilization

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0001714B1 (fr) * 1977-10-26 1984-03-21 The Post Office Appareil de commande pour un dispositif laser à semi-conducteur
US4622672A (en) * 1984-01-20 1986-11-11 At&T Bell Laboratories Self-stabilized semiconductor lasers
DE3421851C2 (de) * 1984-06-13 1997-12-18 Sfim Ind Deutschland Gmbh Verfahren zur Wellenlängen- und Leistungsregelung der Ausgangsstrahlung einer Halbleiterstrahlungsquelle
US4730112A (en) * 1986-03-07 1988-03-08 Hibshman Corporation Oxygen measurement using visible radiation
SE453034B (sv) * 1986-08-29 1988-01-04 Olle Nilsson Forfarande och anordning for stabilisering av en halvledarlaser med avseende pa dess frekvens och/eller fas

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9106141A1 *

Also Published As

Publication number Publication date
FI921592A (fi) 1992-04-10
SE8903363D0 (sv) 1989-10-13
WO1991006141A1 (fr) 1991-05-02
FI921592A0 (fi) 1992-04-10
SE8903363A (fr) 1991-02-11
AU6547090A (en) 1991-05-16
SE463952B (sv) 1991-02-11

Similar Documents

Publication Publication Date Title
US6040914A (en) Simple, low cost, laser absorption sensor system
US7180595B2 (en) Gas detection method and gas detector device
US5026991A (en) Gaseous species absorption monitor
US5637872A (en) Gas detector
Werle Spectroscopic trace gas analysis using semiconductor diode lasers
US6351309B1 (en) Dual modulation laser line-locking technique for wavelength modulation spectroscopy
JPWO2014106940A1 (ja) ガス吸収分光装置及びガス吸収分光方法
JPH0831648B2 (ja) 周波数安定性監視方法および装置ならびに周波数ロック方法および装置
CN110068548B (zh) 用于离轴积分腔系统中激光器的波长锁定装置及其锁定方法
US4441815A (en) Self-modulating spectrometer
US5930000A (en) Line-locked diode laser for gas spectroscopy
US5640245A (en) Spectroscopic method with double modulation
Modugno et al. Detection of H2S at the ppm level using a telecommunication diode laser
CN110987867B (zh) 用于激光光谱学的光学测量系统中的目标气体的相对定位的方法和系统
KR100316487B1 (ko) 가스중의 불순물의 분광분석방법
EP0495874A1 (fr) Appareil permettant de stabiliser la longueur d'onde d'un faisceau lumineux module par signal
JPH06148072A (ja) ガス濃度測定方法およびその測定装置
JP2744728B2 (ja) ガス濃度測定方法およびその測定装置
US10175166B1 (en) Method for operating an optical measuring system for measuring the concentration of a gas component in a measured gas
Werle et al. High-frequency-modulation spectroscopy: phase noise and refractive index fluctuations in optical multipass cells
JPH03277945A (ja) ガス検知装置
JP2792782B2 (ja) ガス濃度測定方法およびその測定装置
Sano et al. High sensitivity short-path monitoring of trace gases employing PbSnTe tunable diode laser
Uittenbosch et al. Synthetic dispersion interferometry for relative atmospheric pressure sensing
US6243401B1 (en) Methods and apparatus for wavelength measurement and tracking using a semiconductor laser amplifier

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19920408

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB IT LI LU NL SE

17Q First examination report despatched

Effective date: 19931126

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19940407