CN110277725B - Supercontinuum generation method and device with spectral distribution unchanged with power - Google Patents
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- H01S3/1022—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation by controlling the optical pumping
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Abstract
The present invention relates to a supercontinuum generation device, and more particularly, to a supercontinuum generation method and device with spectral distribution unchanged with power. The device comprises a DSR laser, an optical fiber amplifier, a first pump light source, a coupler, a second pump light source and a third pump light source; the invention can obtain the light pulse with constant peak power which is not changed with the change of pumping power, and the required peak power can be adjusted by changing the parameters of devices in the structure; secondly, a supercontinuum with spectral distribution which does not change along with output power can be obtained, and stability, practicability and reliability in the application process are improved; and thirdly, the structure is simple, the operation is easy, the light pulse with constant peak power and no change along with the pumping power and the supercontinuum with spectral distribution and no change along with the output power can be realized through proper pumping power distribution, redundant links are not involved, and the energy utilization rate is high.
Description
Technical Field
The present invention relates to a supercontinuum generation device, and more particularly, to a supercontinuum generation method and device with spectral distribution unchanged with power.
Background
The supercontinuum light source has the advantages of wide spectrum, high brightness, good spatial coherence and the like, has wide application prospect in the aspects of optical measurement, molecular spectroscopy, biomedical imaging, optical biological tissue erosion and the like, and is one of research hot spots in the field of light sources. Currently, supercontinuum is mainly obtained by inputting pulse laser into a nonlinear medium (such as a photonic crystal fiber) for nonlinear broadening, and after the length of the nonlinear medium and the shape and wavelength of a pump pulse are fixed, the spectral distribution of supercontinuum is mainly determined by the peak power of a pulse laser pumping the supercontinuum. Since the pump power affects the peak power of the pulse laser, the variation of the peak power of the pulse laser causes the output spectrum and the output power of the supercontinuum to vary, so that the spectral distribution of the finally excited supercontinuum varies with the variation of the output power thereof. Therefore, how to obtain a supercontinuum whose spectral distribution does not vary with the output power is a technical problem of great concern to researchers in the field, the fundamental approach being to obtain a pulsed laser whose peak power does not vary with the pump power.
Dissipative soliton resonance mode locking (Dissipative Soliton Resonance, DSR) pulses are mode locking pulses that can generate extremely large energy, predicted to occur by theoretical calculations in 2008, and experimentally confirmed in 2009. Theory and experiment show that under the state of dissipative soliton resonance, the pulse can be greatly widened along with the increase of pumping power, but the peak power is maintained unchanged. However, existing DSR lasers suffer from the following drawbacks in applications where directly pumping the nonlinear medium produces a supercontinuum: the power of the existing DSR laser is up to one kilowatt level, and the power is amplified to thousands of watts by a single-stage or multi-stage amplifier to be used as a pumping source of a supercontinuum light source, but the pulse obtained after directly amplifying the DSR laser loses the characteristic that the peak power is not changed along with the pumping power.
The invention can effectively make up the defect of direct amplification of the DSR laser, generate an optical fiber laser with peak power not changing along with pump power, and obtain super-continuous spectrum with spectral distribution not changing along with output power.
Disclosure of Invention
Aiming at the defects of a direct amplification DSR laser, the invention provides a supercontinuum generation method and a supercontinuum generation device with the spectral distribution unchanged along with the power, and aims to solve the technical problems that the peak power of DSR pulse is amplified by a plurality of times or even a plurality of orders of magnitude by distributing the pumping power of the DSR laser and the pumping power of an amplifier to obtain an optical fiber laser with the output pulse peak power unchanged along with the pumping power, and the supercontinuum with the spectral distribution unchanged along with the output power is obtained.
The technical scheme adopted by the invention is as follows: a super-continuum spectrum generation method with spectral distribution unchanged with power aims at a super-continuum spectrum generation device comprising a DSR laser 1, an optical fiber amplifier 2, a first pump light source 3, a coupler 4, a second pump light source 5 and a third pump light source 6, and comprises the following steps:
firstly, parameters of the DSR laser 1 are collected, and the relation between the pumping power and the output pulse width of the DSR laser 1 is calculated:
a set of pump powers and corresponding pulse width data for DSR laser 1 are measured: x0, X1, …, xn and τ 0 ,τ 1 ,…,τ n Wherein X0 is the threshold value of pulse oscillation starting in DSR laser 1 (DSR laser requires a certain pump power to start outputting pulse, the pump power is the threshold value of DSR laser pulse oscillation starting), τ 0 The output pulse width is the pulse width when starting oscillation; calculating the slope k of the relation between the pumping power and the pulse width of the DSR laser 1 according to a linear fitting method by combining the data of the pumping power and the pulse width of the DSR laser 1;
secondly, acquiring parameters of the optical fiber amplifier 2, and calculating the relation between the pumping power of the optical fiber amplifier 2 and the peak power of the output pulse:
optionally adjusting the pumping power of DSR laser 1 to X1 and X2 greater than threshold X0, respectively corresponding to output pulse with pulse width τ 1 And τ 2 The method comprises the steps of carrying out a first treatment on the surface of the The output pulse width of the fixed DSR laser 1 is at tau 1 And τ 2 Measuring the pumping power data of the optical fiber amplifier 2 and the amplified pulse peak power data respectively, and calculating the slope of the relation between the pumping power of the optical fiber amplifier 2 and the amplified pulse peak power according to a linear fitting method; the pulse width is tau according to the relationship that the slope is inversely proportional to the pulse width, and proportional to the pulse period and the amplification efficiency of the optical fiber amplifier 2 1 And τ 2 The following slopes are expressed as:where η represents the amplification efficiency of the optical fiber amplifier 2 and T is the period of the pulse;
according to approximation of pulse width invariance during amplificationRule, pulse width sustain τ during amplification 1 And τ 2 The method comprises the steps of carrying out a first treatment on the surface of the Pulse width τ 1 And τ 2 In this case, the relationship between the peak power of the amplified pulse and the pump power of the optical fiber amplifier 2 is as follows:
x0 is the amplification threshold of the optical fiber amplifier 2 (when the pulse passes through the optical fiber amplifier, since the gain medium in the optical fiber amplifier has certain absorption, the pump power of the optical fiber amplifier needs to be set to a certain value to enable the input pulse peak power not to be amplified nor to be reduced just, the pulse peak power starts to be amplified after the pump power is higher than the value, and the pump power is the amplification threshold of the optical fiber amplifier), and P in Peak power, P of output pulse for DSR laser 1 1 And P 2 Respectively representing pulse width tau 1 And τ 2 The peak power of the amplified pulse of (a), ηTx represents the work done on the pulse when the pump light source acts on the fiber amplifier 2, and the pulse width is τ 1 And τ 2 The pulse peak power variation caused by the pulse of (2) is proportional toAnd
thirdly, calculating a coupling ratio:
the peak power variation of the pulse output from DSR laser 1 after passing through fiber amplifier 2 is (P out -P in )，P out Peak power required; at pulse width tau 1 And τ 2 The pump power variation of the optical fiber amplifier 2 is:
DSR laser 1 outputs pulse width from τ 1 Increasing to τ 2 The pump power variation of DSR laser 1 is:
the coupling ratio of the coupler 4 is the ratio of the variation of the pump powers of the DSR laser 1 and the fiber amplifier 2:
the fourth step produces a supercontinuum:
the pump power of the first pump light source 3 is set to be X0, the pump power of the second pump light source 5 is set to be X0, and the coupling ratio of the coupler 4 is selected to beBy adjusting the third pump light source 6, the DSR laser 1 and the optical fiber amplifier 2 can be powered proportionally, and the super-continuum spectrum with the spectral distribution unchanged with the power can be generated.
Further, the linear fitting method in the first step and the second step is a first-order linear fitting method.
The invention also provides a supercontinuum generation device based on the method, which comprises a DSR laser 1, an optical fiber amplifier 2, a first pumping light source 3, a coupler 4, a second pumping light source 5 and a third pumping light source 6; the output end of the DSR laser 1 is connected with the optical fiber amplifier 2, the output end of the first pumping light source 3 is connected with the DSR laser 1, the pumping power of the first pumping light source 3 is set to be the starting vibration threshold value of the DSR laser 1, the output end of the second pumping light source 5 is connected with the optical fiber amplifier 2, the pumping power of the second pumping light source 5 is set to be the amplifying threshold value of the optical fiber amplifier 2, the coupler 4 is a split-two coupler, the output end of the third pumping light source 6 is connected with the input end of the coupler 4, and the two output ends of the coupler 4 are respectively connected with the DSR laser 1 and the optical fiber amplifier 2; by distributing the pump light power of the third pump light source 6 to the DSR laser 1 and the optical fiber amplifier 2 by the coupling ratio of the coupler 4 calculated in the above manner, a supercontinuum output whose spectral distribution does not vary with power can be produced.
The invention also provides a second supercontinuum generation device based on the method, which comprises a DSR laser 1, an optical fiber amplifier 2, a first pumping light source 3, a coupler 4 and a third pumping light source 6; the output end of the DSR laser 1 is connected with the optical fiber amplifier 2, the output end of the first pumping light source 3 is connected with the DSR laser 1, the pumping light power of the first pumping light source 3 is set to be the starting vibration threshold value of the DSR laser 1, the coupler 4 is a one-to-two coupler, the output end of the third pumping light source 6 is connected with the input end of the coupler 4, and the two output ends of the coupler 4 are respectively connected with the DSR laser 1 and the optical fiber amplifier 2; by distributing the pump light power of the third pump light source 6 to the DSR laser 1 and the optical fiber amplifier 2 by the coupling ratio of the coupler 4 calculated in the above manner, a supercontinuum output whose spectral distribution does not vary with power can be produced. When the amplification threshold of the optical fiber amplifier 2 is far smaller than the pump light provided to the optical fiber amplifier 2 in proportion, the second pump light source 5 is not needed to additionally provide the amplification threshold, and the pump light of the third pump light source 6 can enable the optical fiber amplifier 2 to realize the amplification effect on the peak power of the input pulse as soon as the pump light is started.
The invention also provides a third supercontinuum generation device based on the method, which comprises a DSR laser 1, an optical fiber amplifier 2, a coupler 4, a second pumping light source 5 and a third pumping light source 6; the output end of the DSR laser 1 is connected with the optical fiber amplifier 2, the output end of the second pumping light source 5 is connected with the optical fiber amplifier 2, the coupler 4 is a split-two coupler, the output end of the third pumping light source 6 is connected with the input end of the coupler 4, and the two output ends of the coupler 4 are respectively connected with the DSR laser 1 and the optical fiber amplifier 2; by distributing the pump light power of the third pump light source 6 to the DSR laser 1 and the optical fiber amplifier 2 by the coupling ratio of the coupler 4 calculated in the above manner, a supercontinuum output whose spectral distribution does not vary with power can be produced. When the threshold value of the start-up of the DSR laser 1 is far smaller than the pump light provided to the DSR laser 1 in proportion, the first pump light source 3 is not needed to additionally provide the threshold value of the start-up, and the third pump light source 6 can start to output the pulse by starting the pump light of the DSR laser 1.
The invention also provides a fourth supercontinuum generation device based on the method, which comprises a DSR laser 1, an optical fiber amplifier 2, a coupler 4 and a third pumping light source 6; the output end of the DSR laser 1 is connected with the optical fiber amplifier 2, the coupler 4 is a split-two coupler, the output end of the third pumping light source 6 is connected with the input end of the coupler 4, and the two output ends of the coupler 4 are respectively connected with the DSR laser 1 and the optical fiber amplifier 2; by distributing the pump light power of the third pump light source 6 to the DSR laser 1 and the optical fiber amplifier 2 by the coupling ratio of the coupler 4 calculated in the above manner, a supercontinuum output whose spectral distribution does not vary with power can be produced. When the starting threshold value of the DSR laser 1 and the amplifying threshold value of the optical fiber amplifier 2 are far smaller than the pump light provided in proportion, the starting threshold value and the amplifying threshold value are not needed to be additionally provided by the first pump light source 3 and the second pump light source 5, and the DSR laser 1 can output pulses and the optical fiber amplifier 2 amplifies the pulses when the third pump light source 6 is started.
The invention also provides a fifth supercontinuum generation device based on the method, which comprises a DSR laser 1, an optical fiber amplifier 2, a first pumping light source 3 and a second pumping light source 5; the output end of the DSR laser 1 is connected with the optical fiber amplifier 2, the output end of the first pumping light source 3 is connected with the DSR laser 1, and the output end of the second pumping light source 5 is connected with the optical fiber amplifier 2; by adopting the coupling ratio calculated by the method, the pump light power of the first pump light source 3 and the pump light power of the second pump light source 5 are distributed to the DSR laser 1 and the optical fiber amplifier 2 proportionally, and the supercontinuum output with the spectral distribution unchanged with the power can be generated. In case a suitable proportion of the coupler 4 is not available, the DSR laser 1 and the fiber amplifier 2 are directly pumped in the above-mentioned proportions by the first pump light source 3 and the second pump light source 5.
Further, the DSR laser 1 may be replaced by other kinds of pulsed light sources whose peak power does not vary with the pump power, such as a laser with electrically tunable pulses that are pulse shaped and amplified.
Further, the optical pulse width outputted by the DSR laser 1 ranges from femto seconds to micro seconds, so that the pulse width is almost unchanged when the optical fiber amplifier 2 amplifies the optical fiber, and the peak power of the amplified pulse is linearly increased along with the pumping power of the optical fiber amplifier 2.
Further, in the case where the nonlinear effect of the gain fiber is weak in the fiber amplifier 2, resulting in failure to generate a supercontinuum during amplification, the nonlinear medium 8 needs to be added.
Further, the nonlinear medium 8 includes various optical fibers that can generate nonlinear transformation, such as conventional passive optical fibers, doped optical fibers, microstructured optical fibers (including photonic crystal fibers), tapered optical fibers, and the like.
Further, in the case where there is a strong reflected back light of the nonlinear medium 8, it is necessary to add an isolator 7 between the optical fiber amplifier 2 and the nonlinear medium 8.
Further, the devices in the device are connected through tail fibers.
The invention is based on the following principle: the peak power output when the pulse laser is amplified is proportional to the pump light power of the amplifier. At the same amplifier pump light power, the wide pulse has a lower magnification than the narrow pulse. When the pulse width of the input amplifier is increased, both the wide pulse and the narrow pulse can be amplified to the same peak power by increasing the pump power of the amplifier to energize the increased portion of the pulse. The pulse width of the input amplifier may be varied by increasing or decreasing the pump power of the DSR laser. By increasing the width of the pulses input to the amplifier while increasing the amplifier pump power, or by decreasing the width of the pulses input to the amplifier while decreasing the amplifier pump power, pulses with equal output peak power but different widths can be obtained. Finally, as the peak power of the pulse is constant, the spectrum distribution of the supercontinuum generated by the nonlinear medium is constant, but the output power of the supercontinuum increases with the increase of the pulse energy.
The beneficial effects of the invention are as follows:
firstly, an optical pulse with constant peak power which does not change with the change of pump power can be obtained, and the required peak power can be adjusted by changing the parameters of devices in the structure (such as the coupling ratio of the coupler 4);
secondly, a supercontinuum with spectral distribution which does not change along with output power can be obtained, and stability, practicability and reliability in the application process are improved;
and thirdly, the structure is simple, the operation is easy, the light pulse with constant peak power and no change along with the pumping power and the supercontinuum with spectral distribution and no change along with the output power can be realized through proper pumping power distribution, redundant links are not involved, and the energy utilization rate is high.
Drawings
FIG. 1 is a schematic diagram of a first embodiment of the present invention employing three pump sources and a coupler to provide pumping;
FIG. 2 shows a second embodiment of the present invention, wherein two pump sources and a coupler are used to provide pumping;
FIG. 3 is a third embodiment of the invention employing two pump sources and a coupler to provide pumping;
FIG. 4 is a fourth embodiment of the invention employing a pump source and a coupler to provide pumping;
FIG. 5 shows a fifth embodiment of the present invention, wherein two pump sources are used to provide pumps respectively;
FIG. 6 is a sixth embodiment of the invention, with the addition of a nonlinear medium to produce a supercontinuum, and with the use of an isolator to avoid back reflection when needed;
FIG. 7 is a schematic diagram illustrating the principle of implementing a fiber laser whose peak power does not vary with pump power; (a) A DSR laser pumping power and pulse width corresponding relation diagram (b) a corresponding relation diagram of input pumping light power and output pulse peak power of the optical fiber amplifier;
FIG. 8 is a schematic diagram of the output pulse of the peak power invariant pulse width increase of the present invention;
fig. 9 is a graph of the output supercontinuum of the present invention with peak power unchanged with pump power.
Detailed Description
The invention is further described below with reference to the drawings and the detailed description.
Fig. 1 is a block diagram of an embodiment of the present invention employing three pump sources and a coupler to provide pumping, where DSR laser 1 is connected to a fiber amplifier 2 for amplification. The first pump light source 3 is connected to the DSR laser 1, the power of which is set to the threshold value of the DSR laser 1, and the second pump light source 5 is connected to the optical fiber amplifier 2, the power of which is set to the threshold value of the optical fiber amplifier 2. The third pump light source 6 distributes power via the coupler 4 to energize the DSR laser 1 and the fiber amplifier 2.
Fig. 2 is a block diagram of a second embodiment of the invention, using two pump sources and a coupler to provide pumping, in which DSR laser 1 is connected to fiber amplifier 2 for amplification. The first pump light source 3 is connected to the DSR laser 1, and its power is set to the threshold value of the start of the DSR laser 1. The third pump light source 6 distributes power via the coupler 4 to energize the DSR laser 1 and the fiber amplifier 2. When the amplification threshold of the optical fiber amplifier 2 is now much smaller than the pump light provided in proportion, the second pump light source 5 is not needed.
Fig. 3 is a block diagram of a third embodiment of the invention, again using two pump sources and a coupler to provide pumping, in which DSR laser 1 is connected to fiber amplifier 2 for amplification. The second pump light source 5 is connected to the optical fiber amplifier 2, and its power is set to the amplification threshold of the optical fiber amplifier 2. The third pump light source 6 distributes power via the coupler 4 to energize the DSR laser 1 and the fiber amplifier 2. At this time, the starting threshold of DSR laser 1 is far smaller than the pump light provided in proportion, without the need for first pump light source 3.
Fig. 4 is a block diagram of a fourth embodiment of the invention employing a pump source and a coupler to provide pumping, wherein DSR laser 1 is coupled to fiber amplifier 2 for amplification. At this time, the start-up threshold of DSR laser 1 and the amplification threshold of fiber amplifier 2 are both far smaller than the pump light provided in proportion, without first pump light source 3 and second pump light source 5. The third pump light source 6 distributes power via the coupler 4 to energize the DSR laser 1 and the fiber amplifier 2.
Fig. 5 is a block diagram of a fifth embodiment of the invention, in which two pump sources are used to provide pumping, wherein DSR laser 1 is connected to fiber amplifier 2 for amplification. At this time, a coupler 4 of an appropriate ratio is not available, and the DSR laser 1 and the optical fiber amplifier 2 are respectively connected to the first pump light source 3 and the second pump light source 5, and are supplied with energy in the calculated ratio.
Fig. 6 is a sixth embodiment of the present invention, in which an isolator 7 and a nonlinear medium 8 are added on the basis of the first embodiment; in the case where the nonlinear effect of the gain fiber is weak in the fiber amplifier 2, resulting in failure to generate a supercontinuum during amplification, the nonlinear medium 8 needs to be added. And in the case where there is a strong reflected back light of the nonlinear medium 8, it is necessary to add an isolator 7 between the fiber amplifier 2 and the nonlinear medium 8.
Fig. 7 is a schematic diagram for explaining the principle of realizing an optical fiber laser whose peak power does not vary with the pump power, fig. 7 (a) is a diagram of the correspondence between the pump power and the pulse width of the DSR laser, and fig. 7 (b) is a correspondence between the pump power of the optical fiber amplifier and the peak power of the amplified output pulse. The pulse width τ is shown in FIG. 7 (a) 0 ，τ 1 And τ 2 And corresponding DSR pump power, a width and power relationship expression and slope k are calculated. The solid line in FIG. 7 (b) corresponds to a pulse width τ input to the fiber amplifier 2 1 The dashed line corresponds to a pulse width τ input into the fiber amplifier 2 2 . The ordinate position indicated by the horizontal dashed line indicates that the input pulses of different pulse widths are now amplified to the same peak power, and the corresponding abscissa indicates that the optical fiber amplifier 2 needs to provide pump power values x1 and x2, respectively.
The method of generating a supercontinuum with peak power unchanged with pump power using the above-described apparatus is explained with the aid of fig. 7:
firstly, parameters of the DSR laser 1 are collected, and the relation between the pumping power and the output pulse width of the DSR laser 1 is calculated: a set of pump powers and corresponding pulse width data for DSR laser 1 are measured: x0, X1, …, xn and τ 0 ,τ 1 ,…,τ n The method comprises the steps of carrying out a first treatment on the surface of the Wherein X is 0 For starting pulse oscillation in DSR laser 1Is τ, is equal to the threshold value of (1) 0 The output pulse width is the pulse width when starting oscillation; in combination with the data of the pump power and pulse width of DSR laser 1, and in combination with fig. 7 (a), the slope k of the pump power and pulse width relationship is calculated according to a first order linear fitting method.
Secondly, acquiring parameters of the optical fiber amplifier 2, and calculating the relation between the pumping power of the optical fiber amplifier 2 and the peak power of the output pulse: optionally adjusting the pumping power of DSR laser 1 to X1 and X2 greater than threshold X0, respectively corresponding to output pulse with pulse width τ 1 And τ 2 (τ 1 And τ 2 All within the range of the DSR laser 1 output pulse width); the output pulse width of the fixed DSR laser 1 is at tau 1 And τ 2 And (2) measuring the pumping power data of the optical fiber amplifier 2 and the amplified pulse peak power data respectively, and calculating the slope of the relation between the pumping power of the optical fiber amplifier 2 and the amplified pulse peak power according to a first-order linear fitting method in combination with fig. 7 (b). Combining the slope with the inverse proportion of the pulse width, and the proportional relation of the pulse period and the amplification efficiency of the optical fiber amplifier 2, the pulse width is tau 1 And τ 2 The following slopes are expressed as:where η represents the amplification efficiency of the optical fiber amplifier 2 and T is the period of the pulse.
According to the approximate rule that the pulse width is unchanged in the amplifying process, the pulse width in the amplifying process maintains tau 1 And τ 2 . Pulse width τ 1 And τ 2 The relation between the amplified pulse peak power and the pumping power of the optical fiber amplifier 2 is as follows:
x0 is the amplification threshold, P, of the fiber amplifier 2 in Peak power, P of output pulse for DSR laser 1 1 And P 2 Respectively representing pulse width tau 1 And τ 2 Peak power after pulse amplification of (a). ηTx represents the work done on the pulse when the pump light source acts on the fiber amplifier 2, for pulse width τ 1 And τ 2 The pulse peak power variation caused by the pulse of (2) is proportional toAnd
thirdly, calculating a coupling ratio: the peak power variation of the pulse output from DSR laser 1 after passing through fiber amplifier 2 is (P out -P in )，P out To the peak power required. At pulse width tau 1 And τ 2 The pump power variation of the optical fiber amplifier 2 is:
DSR laser 1 outputs pulse width from τ 1 Increasing to τ 2 The pump power variation of DSR laser 1 is:
the corresponding coupler coupling ratio is the ratio of the variation of the pump powers of the DSR laser 1 and the fiber amplifier 2:
the fourth step produces a supercontinuum: the pump power of the first pump light source 3 is set to be X0, the pump power of the second pump light source 5 is set to be X0, and the coupling ratio of the coupler 4 is selected to beBy adjusting the third pump light source 6, the DSR laser 1 and the optical fiber amplifier 2 can be powered proportionally, and the super-continuum spectrum with the spectral distribution unchanged with the power can be generated.
Fig. 8 is a pulse diagram of the resulting pulse width increase with constant peak power. The system is built according to any of the structures of fig. 1 to 5, and the pulses of the DSR laser are amplified to obtain output pulses with increased pulse width but constant peak power.
Fig. 9 is a graph showing the resulting output supercontinuum with peak power unchanged with pump power. The output end of the optical fiber amplifier 2 in the structures of fig. 1 to 5 and the output end of the optical fiber photonic crystal fiber 8 in fig. 6 can obtain a supercontinuum with the overall increase of the spectral intensity but the stable and unchanged distribution as the output power increases.
Claims (13)
1. A method of supercontinuum generation having a spectral distribution that does not vary with power, the method comprising the steps of:
firstly, collecting parameters of a DSR laser (1), and calculating the relation between pumping power and output pulse width of the DSR laser (1):
measuring a set of pump powers of the DSR laser (1) and corresponding pulse width data: x0, X1, …, xn and τ 0 ,τ 1 ,…,τ n Wherein X0 is the threshold value of pulse initiation in DSR laser (1), τ 0 The output pulse width is the pulse width when starting oscillation; calculating the slope k of the relation between the pumping power and the pulse width of the DSR laser (1) according to a linear fitting method by combining the data of the pumping power and the pulse width of the DSR laser (1);
secondly, parameters of the optical fiber amplifier (2) are collected, and the relation between the pumping power of the optical fiber amplifier (2) and the peak power of the output pulse is calculated:
optionally adjusting the pumping power of DSR laser (1) to X1 and X2 which are larger than threshold value X0, respectively corresponding to the pulse width tau of the output pulse 1 And τ 2 The method comprises the steps of carrying out a first treatment on the surface of the The output pulse width of the fixed DSR laser (1) is at tau 1 And τ 2 Measuring the pumping power data of the optical fiber amplifier (2) and the amplified pulse peak power data respectively, and calculating the slope of the relation between the pumping power of the optical fiber amplifier (2) and the amplified pulse peak power according to a linear fitting method; the pulse width is tau according to the relationship that the slope is inversely proportional to the pulse width, and directly proportional to the pulse period and the amplification efficiency of the optical fiber amplifier (2) 1 And τ 2 The following slopes are expressed as:wherein η represents the amplification efficiency of the optical fiber amplifier (2), and T is the period of the pulse;
according to the approximate rule that the pulse width is unchanged in the amplifying process, the pulse width in the amplifying process maintains tau 1 And τ 2 The method comprises the steps of carrying out a first treatment on the surface of the Pulse width τ 1 And τ 2 The relationship between the peak power of the amplified pulse and the pump power of the optical fiber amplifier (2) is as follows:
x0 is the amplification threshold value of the optical fiber amplifier (2), P in Peak power, P of output pulse for DSR laser (1) 1 And P 2 Respectively representing pulse width tau 1 And τ 2 Wherein ηTx represents work done on the pulse when the pump light source acts on the optical fiber amplifier (2), and τ is the pulse width 1 And τ 2 The pulse peak power variation caused by the pulse of (2) is proportional toAnd
thirdly, calculating a coupling ratio:
the peak power variation of the pulse output by the DSR laser (1) after passing through the optical fiber amplifier (2) is (P) out -P in )，P out Peak power required; at pulse width tau 1 And τ 2 When the pump power variation of the optical fiber amplifier (2) is as follows:
DSR laser (1) outputs pulse width from τ 1 Increasing to τ 2 When the pump power variation of the DSR laser (1) is as follows:
the coupling ratio of the coupler (4) is the ratio of the variable amounts of the pump power of the DSR laser (1) and the optical fiber amplifier (2):
the fourth step produces a supercontinuum:
setting the pumping power of the first pumping light source (3) as X0, setting the pumping power of the second pumping light source (5) as X0, and selecting the coupling ratio of the coupler (4) asThe third pumping light source (6) is adjusted to realize the power supply of the DSR laser (1) and the optical fiber amplifier (2) in proportion, and realize the super-continuum spectrum generation with the spectral distribution unchanged with the power.
2. A method of supercontinuum generation in which the spectral distribution is invariant with power according to claim 1, wherein: the linear fitting method in the first step and the second step is a first-order linear fitting method.
3. A supercontinuum generation device according to the method of claim 1, characterized in that: the device comprises a DSR laser (1), an optical fiber amplifier (2), a first pump light source (3), a coupler (4), a second pump light source (5) and a third pump light source (6); the output end of the DSR laser (1) is connected with the optical fiber amplifier (2), the output end of the first pumping light source (3) is connected with the DSR laser (1), the pumping power of the first pumping light source (3) is set to be the starting vibration threshold value of the DSR laser (1), the output end of the second pumping light source (5) is connected with the optical fiber amplifier (2), the pumping power of the second pumping light source (5) is set to be the amplifying threshold value of the optical fiber amplifier (2), the coupler (4) is a split-two coupler, the output end of the third pumping light source (6) is connected with the input end of the coupler (4), and the two output ends of the coupler (4) are respectively connected with the DSR laser (1) and the optical fiber amplifier (2); by allocating the pump light power of the third pump light source (6) to the DSR laser (1) and the fiber amplifier (2) by the coupling ratio of the coupler (4) calculated according to the method of claim 1, a supercontinuum output is produced whose spectral distribution does not vary with power.
4. A supercontinuum generation device according to the method of claim 1, characterized in that: the device comprises a DSR laser (1), an optical fiber amplifier (2), a first pumping light source (3), a coupler 4 and a third pumping light source (6); the output end of the DSR laser (1) is connected with the optical fiber amplifier (2), the output end of the first pumping light source (3) is connected with the DSR laser (1), the pumping light power of the first pumping light source (3) is set to be the starting vibration threshold value of the DSR laser (1), the coupler (4) is a split-two coupler, the output end of the third pumping light source (6) is connected with the input end of the coupler (4), and the two output ends of the coupler (4) are respectively connected with the DSR laser (1) and the optical fiber amplifier (2); by allocating the pump light power of the third pump light source (6) to the DSR laser (1) and the fiber amplifier (2) by the coupling ratio of the coupler (4) calculated according to the method of claim 1, a supercontinuum output is produced whose spectral distribution does not vary with power.
5. A supercontinuum generation device according to the method of claim 1, characterized in that: the device comprises a DSR laser (1), an optical fiber amplifier (2), a coupler (4), a second pumping light source (5) and a third pumping light source (6); the output end of the DSR laser (1) is connected with the optical fiber amplifier (2), the output end of the second pumping light source (5) is connected with the optical fiber amplifier (2), the coupler (4) is a split-two coupler, the output end of the third pumping light source (6) is connected with the input end of the coupler (4), and the two output ends of the coupler (4) are respectively connected with the DSR laser (1) and the optical fiber amplifier (2); by allocating the pump light power of the third pump light source (6) to the DSR laser (1) and the fiber amplifier (2) by the coupling ratio of the coupler (4) calculated according to the method of claim 1, a supercontinuum output is produced whose spectral distribution does not vary with power.
6. A supercontinuum generation device according to the method of claim 1, characterized in that: comprises a DSR laser (1), an optical fiber amplifier (2), a coupler (4) and a third pumping light source (6); the output end of the DSR laser (1) is connected with the optical fiber amplifier (2), the coupler (4) is a split-two coupler, the output end of the third pumping light source (6) is connected with the input end of the coupler (4), and the two output ends of the coupler (4) are respectively connected with the DSR laser (1) and the optical fiber amplifier (2); by allocating the pump light power of the third pump light source (6) to the DSR laser (1) and the fiber amplifier (2) by the coupling ratio of the coupler (4) calculated according to the method of claim 1, a supercontinuum output is produced whose spectral distribution does not vary with power.
7. A supercontinuum generation device according to the method of claim 1, characterized in that: comprises a DSR laser (1), an optical fiber amplifier (2), a first pumping light source (3) and a second pumping light source (5); the output end of the DSR laser (1) is connected with the optical fiber amplifier (2), the output end of the first pumping light source (3) is connected with the DSR laser (1), and the output end of the second pumping light source (5) is connected with the optical fiber amplifier (2); the coupling ratio calculated by the method of claim 1 is adopted to distribute the pump light power of the first pump light source (3) and the second pump light source (5) to the DSR laser (1) and the optical fiber amplifier (2) proportionally, so that the supercontinuum output with the spectral distribution unchanged with the power can be generated.
8. A supercontinuum generation device according to any one of claims 3 to 7, characterized in that: the DSR laser (1) adopts a laser with electric modulation pulse subjected to pulse shaping and amplification.
9. A supercontinuum generation device according to any one of claims 3 to 7, characterized in that: the light pulse width range output by the DSR laser (1) is from femtosecond to microsecond, so that the pulse width is almost unchanged when the light pulse is amplified in the optical fiber amplifier (2), and the peak power of the amplified pulse is linearly increased along with the pumping power of the optical fiber amplifier (2).
10. A supercontinuum generation device according to any one of claims 3 to 7, characterized in that: in the case that the nonlinear effect of the gain fiber is weak in the fiber amplifier (2), and a supercontinuum cannot be generated in the amplification process, a nonlinear medium (8) needs to be added.
11. A supercontinuum generation device according to claim 10, characterized in that: the nonlinear medium (8) comprises a conventional passive optical fiber, a doped optical fiber, a microstructured optical fiber and a tapered optical fiber.
12. A supercontinuum generation device according to claim 10, characterized in that: in case of a strongly reflected back light of the nonlinear medium (8), an isolator (7) needs to be added between the fiber amplifier (2) and the nonlinear medium (8).
13. A supercontinuum generation device according to any one of claims 3 to 7, characterized in that: the devices in the device are connected through tail fibers.
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