Control apparatus and control method for optical pulse output sequence

Abstract

A control apparatus and control method for an optical pulse output sequence. The control apparatus comprises a beam splitter (4), a carrier-envelope phase detection unit (5) and a chirp coefficient adjustment unit (6), wherein the beam splitter (4) is located on an optical pulse transmission path, and splits an optical pulse into at least output light and monitoring light; the carrier-envelope phase detection unit (5) monitors, by means of receiving the monitoring light, an offset of a carrier-envelope phase (CEP) of the output light to form feedback information, and transfers the feedback information to the chirp coefficient adjustment unit (6); and the chirp coefficient adjustment unit (6) stabilizes the carrier-envelope phase (CEP) of the output light by means of adjusting the group-velocity dispersion of a grating (7) located on an optical fiber (3). The control apparatus and control method can control group-velocity dispersion to compensate for an offset of a carrier-envelope phase (CEP) by means of adjusting a chirp coefficient of a grating (7) on an optical fiber, thereby adjusting and stabilizing the carrier-envelope phase (CEP) of emergent light in real time, and improving the stability of a system; in addition, the structure is simple and flexible and is easily integrated.

Description

Control device and control method for optical pulse output sequence Technical Field

[0001] The present invention relates to the field of optical devices, and in particular to a control device and a control method for an optical pulse output sequence. Background Art

[0002] Carrier-envelope phase (CEP) refers to the relationship between the carrier (electromagnetic wave) and envelope (intensity envelope) of an optical pulse, that is, the phase. During the interaction between an optical pulse and matter, CEP largely determines the instantaneous electric field strength of the pulse. In experiments related to instantaneous electric field strength, different CEPs will lead to different physical phenomena, such as attosecond physics and high-harmonic cutoff energy. CEP is also extremely important in the fields of optical atomic clocks, quantum coherent control, and optical frequency combs. CEP stabilization methods are divided into active and passive methods. Active CEP stabilization methods measure and feedback the system's carrier phase drift (CEO), and then make corresponding adjustments based on the feedback results. The advantage of the active CEP control method is that the control of CEP is precise and stable. The disadvantage is that real-time measurement and feedback are difficult to achieve under the kHz repetition rate and high energy amplification mode. Passive CEP stabilization includes control using the difference frequency process (Physical Review Letters, Vol. 88, No. 13, 133901, 2002) and optical parametric amplification (OPA) (Optics Express, Vol. 14, No. 21, 10109-10116). The disadvantage of passive CEP control is that CEP can drift with factors such as the environment, crystal temperature, and beam direction.

[0003] Summary of the Invention

[0004] To overcome the above-mentioned deficiencies of the prior art, the present invention provides a control device and method for an optical pulse output sequence, which adopts an active CEP stabilization method, adjusts the chirp coefficient of the fiber Bragg grating, and compensates the CEP offset by controlling the group velocity dispersion of the light, thereby stabilizing the CEP of the output light.

[0005] On the one hand, the present invention provides a control device for an optical pulse output sequence, the control device for an optical pulse output sequence comprising a beam splitter, a carrier-envelope phase detection unit, and a chirp coefficient adjustment unit, wherein the beam splitter is located on the optical pulse transmission path and at least divides the optical pulse into output light and monitoring light; the carrier-envelope phase detection unit receives the monitoring light, monitors the carrier-envelope phase offset of the output light, forms feedback information, and transmits the feedback information to the chirp coefficient adjustment unit; the chirp coefficient adjustment unit adjusts the chirp coefficient of a grating located on the optical fiber, thereby adjusting the group velocity dispersion of the light in the grating area, thereby stabilizing the carrier-envelope phase of the output light.

[0006] Furthermore, the optical fiber is provided with a grating composed of multiple refractive index modulation periods. A chirp coefficient adjustment unit is disposed on the outer surface of the optical fiber corresponding to the grating region. The light transmitted through the optical fiber has a certain bandwidth, and light of different wavelengths is reflected at different positions on the grating. A correspondence between the input wavelength and the grating position is established based on the input wavelength bandwidth. The carrier envelope phase (CEP) detection unit monitors and records the output light carrier envelope phase (CEP) offset, generating feedback information. Based on this feedback information, the chirp coefficient adjustment unit is adjusted in real time. By adjusting the chirp coefficient of the grating corresponding to the wavelength bandwidth, the group velocity dispersion of the light in the grating region of the optical fiber is adjusted, thereby stabilizing the carrier envelope phase (CEP) of the output light.

[0007] Furthermore, the chirp coefficient adjustment unit is specifically a piezoelectric ceramic array, which adjusts the chirp coefficient of the grating by applying different voltages to the piezoelectric ceramics in different areas, and stabilizes the CEP of the output light by compensating the CEP offset through dispersion.

[0008] Furthermore, the control device further includes a plurality of groups of identical control modules, one group of control modules corresponds to one piezoelectric ceramic, and different voltages are applied to the corresponding piezoelectric ceramics through the control modules.

[0009] Furthermore, after passing through the beam splitter, the ratio of the output light to the monitoring light ranges from 1:1 to 99:1.

[0010] Furthermore, the periods of the gratings are the same; or, the periods of the gratings are different, specifically, the period gradually increases or decreases along the transmission direction of the light.

[0011] In another aspect, the present invention provides a method for controlling an optical pulse output sequence, which relates to carrier-envelope phase locking during optical propagation in an optical fiber. The method includes placing a beam splitter on the optical pulse transmission path, using the beam splitter to split the optical pulse into output light and monitoring light; using a carrier-envelope phase detection unit to receive the monitoring light, monitor the carrier-envelope phase offset of the output light, generate feedback information, and transmit the feedback information to a chirp coefficient adjustment unit; and using the chirp coefficient adjustment unit to adjust the chirp coefficient of a grating located on the optical fiber, thereby adjusting the group velocity dispersion of the light in the grating region, thereby stabilizing the carrier-envelope phase of the output light.

[0012] Furthermore, the optical fiber is provided with a grating composed of multiple grating lines. A chirp coefficient adjustment unit is fixedly mounted on the outer surface of the optical fiber corresponding to the grating region. The light transmitted through the optical fiber has a certain bandwidth, and light of different wavelengths is reflected at different positions on the grating. Based on the different input wavelength bandwidths, a correspondence between the input wavelength and the grating position is established. The carrier envelope phase offset of the output light is monitored and recorded by a carrier envelope phase detection unit to generate feedback information. Based on this feedback information, the chirp coefficient adjustment unit is adjusted in real time. By adjusting the chirp coefficient at the grating position corresponding to the wavelength bandwidth, the group velocity dispersion of the light in the optical fiber is adjusted, thereby stabilizing the carrier envelope phase of the output light.

[0013] Furthermore, the chirp coefficient adjustment unit is specifically a piezoelectric ceramic array, and the chirp coefficient of the grating is adjusted by applying different voltages to the piezoelectric ceramics in different areas.

[0014] The control device and method described above can be used to adjust the chirp coefficient of the fiber Bragg grating (FBG) to control the group velocity dispersion compensation (CEP) offset, thereby stabilizing the CEP of the output light. This device and method offer advantages such as real-time adjustment of the CEP of the output light, improved system stability, and a simple, flexible, and easily integrated structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG1 is a schematic diagram of a control device for an optical pulse output sequence according to the present invention;

[0016] FIG2 is a schematic diagram showing the positional relationship between the grating and the chirp coefficient adjustment unit of the present invention;

[0017] FIG3 is a diagram showing the relationship between the group velocity dispersion formed in Example 1 and the rate of change of the voltage applied to the piezoelectric ceramic in the grating region;

[0018] FIG4 is a diagram showing the relationship between the group velocity dispersion formed in Example 2 and the rate of change of the voltage applied to the piezoelectric ceramic in the grating region;

[0019] FIG5 is a diagram showing the relationship between the group velocity dispersion formed in Example 3 and the rate of change of the voltage applied to the piezoelectric ceramic in the grating region;

[0020] FIG6 is a graph showing the relationship between the group velocity dispersion formed in Example 4 and the rate of change of the voltage applied to the piezoelectric ceramic in the grating region;

[0021] FIG7 is a graph showing the relationship between the group velocity dispersion formed in Example 5 and the rate of change of the voltage applied to the piezoelectric ceramic in the grating region;

[0022] FIG8 is a graph showing the relationship between the group velocity dispersion formed in Example 6 and the rate of change of the voltage applied to the piezoelectric ceramic in the grating region;

[0023] Among them, 1 is a saturable absorber, 2 is a coupler, 3 is an optical fiber, 4 is a beam splitter, 5 is a carrier envelope phase detection unit, 6 is a chirp coefficient adjustment unit, and 7 is a grating. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] As shown in Figure 1, the pulse emitted by the saturable absorber 1 is coupled into the optical fiber 3 through the coupler 2; the optical fiber 3 is provided with a grating 7, which is composed of multiple grating lines. The outer surface of the optical fiber 3 corresponding to the grating 7 is provided with a chirp coefficient adjustment unit 6. The light propagates in the optical fiber 3, passes through the grating 7, and is divided into two light paths by the beam splitter 4 after passing through the grating 7. One light path is used as the output light, and the other light path is used as the monitoring light. The monitoring light is input to the carrier envelope phase detection unit 5, and the carrier envelope phase detection unit 5 monitors and records the CEP offset of the output light and forms feedback information; and based on the feedback information, the chirp coefficient adjustment unit 6 is adjusted in real time. By adjusting the chirp coefficient of the grating 7, the group velocity dispersion of the light in the grating area is adjusted, thereby stabilizing the CEP of the output light.

[0026] The carrier envelope phase detection unit 5 may include any device in the prior art that can measure the carrier envelope phase, such as ultrashort pulse generation and control, supercontinuum optical device, f-2f module, etc.

[0027] The chirp coefficient adjustment unit 6 is specifically a piezoelectric ceramic array. By applying different voltages to the piezoelectric ceramics in different areas, the chirp coefficient of the grating 7 is adjusted, and the CEP offset is compensated by dispersion to stabilize the CEP of the output light.

[0028] Furthermore, optical fiber 3 is provided with a grating 7, and a chirp coefficient adjustment unit 6 is disposed on the outer surface of optical fiber 3 corresponding to the region of grating 7. The grating is composed of multiple refractive index modulation periods. The light transmitted in optical fiber 3 has a certain bandwidth, and light of different wavelengths is reflected at different positions of grating 3. Based on the different input wavelength bandwidths, a correspondence between the input wavelength and the position of grating 7 is established. The carrier envelope phase offset of the output light is monitored and recorded by the carrier envelope phase detection unit 5 to generate feedback information. Based on this feedback information, the chirp coefficient adjustment unit 6 is adjusted in real time. By adjusting the chirp coefficient of grating 7 corresponding to the wavelength bandwidth, the group velocity dispersion of the light in the optical fiber is adjusted, thereby stabilizing the carrier envelope phase (CEP) of the output light.

[0029] Furthermore, the control device further includes a plurality of groups of identical control modules, one group of control modules corresponds to one piezoelectric ceramic, and different voltages are applied to the corresponding piezoelectric ceramics through the control modules.

[0030] Furthermore, after passing through the beam splitter 4 , the ratio of the output light to the monitoring light ranges from 1:1 to 99:1.

[0031] Furthermore, the periods of the gratings 7 are the same; or, the periods of the gratings 7 are different, specifically, the periods gradually increase or decrease along the transmission direction of light.

[0032] When an optical pulse is output, environmental factors such as temperature, humidity, and vibration may cause CEP drift, i.e., a relative deviation between the pulse envelope and the phase occurs, with the phase possibly lagging behind or advancing the pulse envelope. At this point, the output pulse is monitored in real time. When CEP drift is detected, if the phase lags behind the pulse envelope, the chirp coefficient adjustment unit 6 is controlled to adjust the chirp coefficient of the grating 7 to compensate for the group velocity dispersion of the light. When negative group velocity dispersion is provided, the phase of the output pulse is positively excited, thereby correcting the phase drift that lags behind the pulse envelope. Conversely, if the phase drifts ahead of the pulse envelope, the chirp coefficient adjustment unit 6 is controlled to adjust the chirp coefficient of the grating 7 to compensate for the group velocity dispersion of the light. When positive group velocity dispersion is provided, the phase of the output pulse is negatively excited, thereby correcting the phase drift that lags behind the pulse envelope.

[0033] Where: the grating length is l, in meters; the piezoelectric ceramic length is ll, in meters; the number of piezoelectric ceramics is q, q = l / ll, in units; the operating voltage range of the piezoelectric ceramics is 0 to Umax, in V; when the maximum operating voltage Umax is applied, the corresponding maximum deformation of the piezoelectric ceramic is a, where a is in meters;

[0034] From this, we can know that the deformation coefficient of the piezoelectric ceramic is X=a / Umax, where X is in m / V;

[0035] The maximum voltage change rate of the piezoelectric ceramic in the grating area is Xu, where the unit of Xu is V / m: Xu=(U1-U2) / l

[0036] Among them, U1 is the maximum voltage actually applied to the piezoelectric ceramic, and U2 is the minimum voltage actually applied to the piezoelectric ceramic. The unit of U1 and U2 is V.

[0037] It can be obtained that the voltage change rate XXu of the piezoelectric ceramic in the grating area can be in the range of -Xu to +Xu;

[0038] The length change rate of the piezoelectric ceramic in the grating area XX=X*XXu, which is a dimensionless parameter;

[0039] The grating chirp coefficient is C, in nm / cm, where C = W*(XX / ll)*1e7

[0040] Where W is the initial wavelength of the grating, in m;

[0041] Dispersion parameter D = 2*n / ((C*1e-7)*c), where D is expressed in s / m, where c is the speed of light and the default value is 3*1e8m / s

[0042] Finally, we get the group velocity dispersion beta2, beta2 = -D*((W)^2 / (2*π*c)), in s 2 ;

[0043] When a phase drift behind the pulse envelope is detected, the chirp coefficient adjustment unit 6 is controlled to adjust the group velocity dispersion of the grating 7. When a negative group velocity dispersion is provided, the phase of the output pulse is positively excited, thereby correcting the phase drift behind the pulse envelope. Conversely, if a phase drift ahead of the pulse envelope occurs, the chirp coefficient adjustment unit 6 is controlled to adjust the group velocity dispersion of the grating 7. When a positive group velocity dispersion is provided, the phase of the output pulse is negatively excited, thereby correcting the phase drift ahead of the pulse envelope. Different input conditions can provide different degrees of group velocity dispersion control effects, as shown in the following embodiments.

[0044] Examples 1-6

[0045] In Examples 1-6,

[0046] Fiber refractive index: n = 1.46;

[0047] Double optical interference area length D = 1*10 -2 m

[0048] The values ​​of the grating length l, the piezoelectric ceramic length ll, the maximum voltage U1 actually applied to the piezoelectric ceramic, the minimum voltage U2 actually applied to the piezoelectric ceramic, and the grating initial wavelength W are shown in Table 1:

[0049] Table 1

[0050] See Figures 3 to 8, where the horizontal axis is the rate of change of the voltage applied to the piezoelectric ceramic in the grating area, which is a dimensionless parameter, and the vertical axis is the group velocity dispersion, in s. 2 When the piezoelectric ceramic length and the applied voltage range change, the group velocity dispersion responds to different orders of magnitude with the rate of change of the voltage applied to the piezoelectric ceramic in the grating region. The smaller the rate of change, the greater the dispersion introduced. In actual operation, the actual CEP drift can be monitored to select appropriate adjustment parameters and perform real-time adjustment of the output optical pulse, thereby actively adjusting and stabilizing the CEP of the output light.

[0051] It should be noted that the terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0052] In addition, the terms "comprises" and "comprising" and any variations thereof are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, product, or apparatus.

[0053] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of an element or feature to other elements or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the elements in use or operation in addition to the orientations described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The element can also be positioned in other different ways, such as rotated 90 degrees or in other orientations, and the spatially relative descriptions used here are interpreted accordingly.

[0054] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A control device for an optical pulse output sequence, characterized in that: The invention comprises a beam splitter, a carrier envelope phase detection unit and a chirp coefficient adjustment unit, wherein the beam splitter is located on the optical pulse transmission path and at least divides the optical pulse into output light and monitoring light; the carrier envelope phase detection unit monitors the carrier envelope phase offset of the output light by receiving the monitoring light, forms feedback information, and transmits the feedback information to the chirp coefficient adjustment unit; the chirp coefficient adjustment unit adjusts the chirp coefficient of the grating located on the optical fiber, thereby adjusting the group velocity dispersion of the light in the grating area, thereby stabilizing the carrier envelope phase of the output light; the optical fiber is provided with a grating, the grating is composed of a plurality of refractive index modulation periods, the chirp coefficient adjustment unit is fixedly arranged on the outer surface of the optical fiber corresponding to the grating area, the light transmitted in the optical fiber has a certain bandwidth, and light of different wavelengths is reflected at different positions of the grating; according to different input wavelength bandwidths, a corresponding relationship between the input wavelength and the grating position is established, and the output light carrier envelope phase offset is monitored and recorded by the carrier envelope phase detection unit to form feedback information; Based on the feedback information, the chirp coefficient adjustment unit is adjusted in real time. By adjusting the chirp coefficient of the grating, the chirp coefficient of the grating on the optical fiber is adjusted, and then the group velocity dispersion of the light in the grating area is adjusted, thereby stabilizing the carrier envelope phase of the output light; the chirp coefficient adjustment unit is specifically a piezoelectric ceramic array, and the chirp coefficient of the grating is adjusted by applying different voltages to the piezoelectric ceramics in different areas.

2. The control device as claimed in claim 1, further comprising a plurality of groups of identical control modules, wherein one group of control modules corresponds to one piezoelectric ceramic, and different voltages are applied to the corresponding piezoelectric ceramics through the control modules.

3. The control device as described in claim 1, after passing through the beam splitter, the ratio of the output light to the monitoring light ranges from 1:1 to 99:

1.

4. The control device as described in claim 1, wherein the periods of the gratings are the same; or, the periods of the gratings are different, specifically, the period gradually increases or decreases along the transmission direction of the light.

5. A control method for an optical pulse output sequence, comprising: setting a beam splitter on an optical pulse transmission path, using the beam splitter to divide the optical pulse into an output light and a monitoring light; using a carrier envelope phase detection unit to receive the monitoring light, monitoring the carrier envelope phase offset of the output light, forming feedback information, and transmitting the feedback information to a chirp coefficient adjustment unit; using the chirp coefficient adjustment unit to adjust the chirp coefficient of a grating located on an optical fiber, thereby adjusting the group velocity dispersion of light in the grating region, thereby stabilizing the carrier envelope phase of the output light; setting a grating on the optical fiber, the grating consisting of a plurality of grating lines, and fixing a chirp coefficient adjustment unit on the outer surface of the optical fiber corresponding to the grating region, and the light transmitted in the optical fiber has With a certain bandwidth, light of different wavelengths is reflected at different positions of the grating; according to different input wavelength bandwidths, a corresponding relationship between the input wavelength and the grating position is established, and the output light carrier envelope phase offset is monitored and recorded according to the carrier envelope phase detection unit to form feedback information; based on the feedback information, a chirp coefficient adjustment unit is adjusted in real time, and the chirp coefficient of the grating in the optical fiber is adjusted by adjusting the chirp coefficient of the grating position corresponding to the wavelength bandwidth of the saturable absorber, thereby adjusting the group velocity dispersion of the light in the grating area, and then stabilizing the carrier envelope phase of the output light; the chirp coefficient adjustment unit is specifically a piezoelectric ceramic array, and the chirp coefficient of the grating is adjusted by applying different voltages to the piezoelectric ceramics in different areas.

6. The control method as described in claim 5, wherein after passing through the beam splitter, the ratio of the output light to the monitoring light ranges from 1:1 to 99:1.

Images