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
  • H01S5/02—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
  • H01S5/02—Structural details or components not essential to laser action
  • H01S5/024—Arrangements for thermal management
  • H01S5/02453—Heating, e.g. the laser is heated for stabilisation against temperature fluctuations of the environment
• • 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
  • H01S5/06804—Stabilisation of laser output parameters by monitoring an external parameter, e.g. temperature
• • 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
  • H01S5/06808—Stabilisation of laser output parameters by monitoring the electrical laser parameters, e.g. voltage or current
• • 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 relates to an operating temperature or wavelength stabilized semiconductor laser diode with an integrated temperature control part.
• the conventional semiconductor laser diode has been known since 1962, when two research groups independently and almost simultaneously demonstrated GaAs laser diodes. However, it took a long time to get the first laser diodes that still required nitrogen cooling into devices transform that could solve the seemingly simple task of emitting a continuous laser beam at room temperature.
• the wavelength (peak wavelength) which is emitted by a laser diode depends not only on the operating current but also very strongly on the operating temperature. (Unless expressly defined otherwise, "temperature” in the following text always means the operating temperature of the laser diode or the laser chip.) Typical values for the temperature drift are about 0.25 nm / ° C. for GaAlAs and about 0.5 nm / ° C for InGaAsP laser diodes.
• the fact is complicated by the fact that many diode lasers can oscillate simultaneously in several different modes, each with a different wavelength. If the temperature changes, the laser can e.g. B. jumping from one longitudinal mode to another ("mode hopping") and abruptly changing its (peak) wavelength. This can take place if the pulse length changes in the pulsed mode, or if the operating current and output power change during the continuous mode.
• active temperature control which keeps the laser diodes at a fixed temperature, can help to minimize many of the problems mentioned above.
• the object of the invention is to construct a laser diode for the purpose of wavelength stabilization and / or power stabilization, the operating temperature of which is kept at a fixed value which can be set by the user by means of active temperature control.
• the present invention has, inter alia, the task of reducing or miniaturizing all the components required for temperature control and integrating them in a housing of conventional size in addition to the laser chip.
• heat sink large surface area (possibly supported by fans),
• the invention is based on the surprising finding that suitable temperature control of the laser diode, or rather the laser chip, is also made possible by using thermistors.
• this is done by using PTC resistors ("PTC resistors” or “PTCs” for short), which are used as heating and / or regulating elements.
• PTC resistors PTC resistors
• PTCs PTC resistors
• the temperature of the laser chip is "heated up" to a value above the ambient temperature. In general, this temperature value cannot be achieved simply by heating the laser chip by flowing the operating current.
• PTCs can also be used as control elements.
• the laser chip heats the PTC to its operating temperature, while the PTC only serves to regulate this temperature.
• a miniaturized PTC is brought into thermal contact with the laser chip.
• the PTC replaces the "mounting column" on which the laser chip is normally attached and which usually also acts as a heat sink.
• thermocouples e.g. NiCr-Ni
• miniaturized thermistors also called “NTC resistance” or “NTC” for short
• NTC resistance or “NTC” for short
• an NTC can be brought into the area of the laser chip or attached directly to it.
• NTCs can be placed on the PTC, the buffer (see below) and (if the buffer and the housing are thermally insulated from each other) on the housing.
• a suitable buffer is placed between the PTC and the laser chip.
• a buffer z. B. serve a disc made of metal, the size ia between the size of PTCs and the laser chip.
• Said buffer can also be designed in such a way that it simultaneously serves as a carrier which enables the laser chip and the miniaturized PTC to be attached. Buffer or carrier material should be in thermal equilibrium with the laser chip and PTC.
• the laser chip temperature, PTC temperature and housing / buffer temperature can be set in a highly stabilized manner using special control electronics.
• the PTC is heated up and then with an adjustable time delay, the operating current (forward current) of the laser diode is switched on.
• the reverse process is also possible. Accordingly, the operating current of the laser diode is first switched on with a time delay and then the PTC heater is switched on.
• a suitable photodiode can be installed in the region of the radiation emerging from the rear of the laser chip. In contrast to conventional laser diodes, however, this is not absolutely necessary in the context of the present invention for checking the optical output power, since here the laser chip itself can be used both as a radiation detector and as a temperature sensor.
• the current from the photodiode either to control the temperature or to control the optical output power of the laser diode. It is also possible to use the relationship between the change in the optical output power of the laser diode and the current generated by the photodiode for the relative temperature measurement or for temperature calibration.
• the device according to the invention can, depending on the application, windows, filters or special lenses (systems) such as e.g. Gradient index lenses included.
• the above-mentioned components are accommodated in a housing, the size of which corresponds to the standard housings used today.
• the housing is hermetically sealed at the same time.
• the housing for protecting the laser chips against undesired oxidation can also contain inert gases.
• the housing of the modified laser diode can be folded or provided with slots or ribs to enlarge the surface and thus for cooling the same.
• a plurality of laser chips can also be arranged on a PTC or a laser chip between two or more PTCs. Simultaneous use of PTCs and miniaturized Peltier elements is also conceivable.
• the modified laser diode according to the invention can work both in continuous wave and in pulse mode.
• pulse operation is started after a certain time t (warm-up phase).
• Pulse duration t reaches the optical output power of the laser chip from zero or a non-zero level to a maximum value and then drops again to zero or a non-zero power level.
• the pulse height I is referred to in the text below as the mean optical output power during the time t.
• the operating current of the laser diode is brought to a certain maximum smax during the time t, from which it subsequently reaches zero (see above) or a value smm other than zero. drops, s .n is usually in the area of the threshold
• the laser diode according to the invention can be used in all areas in which laser diodes are used today. Numerous new application possibilities open up by combining the laser chip and the temperature control part into a single, highly integrated component.
• the laser diode according to the invention will be used wherever a maximum degree of wavelength stability is required. This is the case, inter alia, when using laser diodes for certain analysis tasks, such as, for example, use in the analysis of human tissue, in particular in the in-vivo examination of body fluids, and very particularly in the non-invasive determination of components of human blood (blood glucose , Cholesterol, alcohol etc.)
• the modified laser diode according to the invention is particularly suitable for use as a radiation source in a device for the qualitative and / or quantitative determination of a sample to be analyzed according to DE patent application P 42 27 813.9, which in turn is mainly used for the non-invasive determination of components of human blood ( Blood glucose, etc.) is used.
• the pulse height of the optical output power of the laser diode according to the invention can be changed in the following manner in pulse mode.
• the second pulse has a pulse height I P__ ⁇ ⁇
• Pulse applies I 2 > I _> I., Etc.
• I pn-1 ⁇ """nn ⁇ ""” min "applies after a sequence of n pulses I 1 to I is followed by the next sequence, starting again with I 1 , etc.
• all parameters relevant to the respective measurement task are measured for each pulse height, but in particular also the temperatures of the laser chip T .., of the PTC T p ⁇ and the housing T_j.
• all relevant measured variables X at I p . and I_. jn are used for calibration (analysis). This is done by looking at the ⁇ X p . about the I p .
• This method has the advantage that only one sample is required for calibration (one-sample calibration). To increase the reliability of the calibration, it should be possible to dilute or enrich the analysis sample. If the concentration of glucose in human blood is determined, a personal calibration curve specific to the patient can be created, for example, by taking blood only once.
• measurements are carried out in the area of the middle of the calibration curve, since the measurement error is smallest there due to the mathematics on which the linear regression is based.
• the center is also far enough away from the background (noise) to avoid its disruptive influence.
• a recalibration sample can be obtained, for example, as follows: Artificial material (e.g. cardboard) can be found that is used for certain I. the same ⁇ X p . causes like a certain concentration of a selected substance (eg glucose) in a sample to be analyzed. When measuring with, for example, a suitable calibration cardboard, this enables the measuring device to be recalibrated at any time, since here the calibration cardboard takes over the role of the substance sought. A calibration-free calibration or, in other words, an indirect calibration method is thus obtained.
• Artificial material e.g. cardboard
• a selected substance eg glucose

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

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

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ID=6471153

Family Applications (1)

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Citations (10)

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• 1992
  • 1992-10-24 DE DE4235768A patent/DE4235768A1/de not_active Ceased
• 1993
  • 1993-10-23 CN CN93120249A patent/CN1094543A/zh active Pending
  • 1993-10-23 TW TW082108911A patent/TW246751B/zh not_active IP Right Cessation
  • 1993-10-25 US US08/424,399 patent/US5680410A/en not_active Expired - Lifetime
  • 1993-10-25 WO PCT/DE1993/001013 patent/WO1994010728A1/de active Application Filing

Patent Citations (10)

Non-Patent Citations (10)

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