CN114967274A - Wide-temperature frequency multiplication conversion method based on quasi-phase matching - Google Patents
Wide-temperature frequency multiplication conversion method based on quasi-phase matching Download PDFInfo
- Publication number
- CN114967274A CN114967274A CN202210381059.4A CN202210381059A CN114967274A CN 114967274 A CN114967274 A CN 114967274A CN 202210381059 A CN202210381059 A CN 202210381059A CN 114967274 A CN114967274 A CN 114967274A
- Authority
- CN
- China
- Prior art keywords
- crystal
- temperature
- quasi
- phase matching
- nonlinear optical
- 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.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/3501—Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals
- G02F1/3509—Shape, e.g. shape of end face
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/355—Non-linear optics characterised by the materials used
- G02F1/3551—Crystals
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/37—Non-linear optics for second-harmonic generation
Abstract
The invention provides a wide-temperature frequency multiplication conversion method based on quasi-phase matching, which comprises a piece of periodic polarization crystal, wherein the phase mismatch amount in the nonlinear optical crystal is approximately in linear relation with the temperature of the crystal, and the second-order partial derivative of the phase mismatch amount to the temperature is far larger than the first-order partial derivative. By reasonably designing the cutting angle and the polarization period of the nonlinear optical crystal, the quasi-phase matching condition is met, and the first-order partial derivative of the phase mismatch quantity to the temperature is zero, so that the frequency conversion efficiency is basically not influenced by the temperature change of the crystal. By changing the cutting angle of the traditional polarization crystal, the nonlinear optical frequency conversion keeps higher conversion efficiency in a wider temperature range, and the temperature adaptability and stability of the nonlinear optical frequency conversion crystal device are improved. The invention does not need temperature control equipment, so that the structure of the nonlinear optical frequency conversion crystal device is simpler and more compact, and meanwhile, the energy consumption of the device is reduced, the cost of the device is reduced, and the performance of the device is improved.
Description
Technical Field
The invention relates to the technical field of nonlinear optical frequency conversion crystal devices, in particular to a wide-temperature frequency doubling conversion method based on a polarization crystal.
Background
The quasi-phase matching technology enables laser participating in nonlinear optical frequency conversion to meet the quasi-phase matching condition by periodically changing the polarization direction of the nonlinear optical crystal, can realize the non-critical phase matching, avoids generating space walk-off, can conveniently utilize the maximum effective nonlinear coefficient of the nonlinear optical crystal, and is widely applied to the nonlinear optical frequency conversion. However, like the birefringent phase matching, the quasi-phase matching is also affected by the temperature variation of the crystal, and generally the half width of the temperature peak thereof is small, resulting in poor environmental temperature adaptability.
When the laser with frequency doubling wavelength of 1064nm in the PPKTP crystal with the traditional cutting angle is used, the half width of the temperature peak value is lower, so that the temperature stability of the frequency doubling laser is poor, and when the environmental temperature slightly deviates from the matching temperature, the power of the frequency doubling laser is sharply reduced. This feature limits its application in environments with varying temperatures, and the current solution is to control the crystal thermostatically, which however increases the system energy consumption and complexity.
Disclosure of Invention
Compared with the existing frequency conversion technology, the wide-temperature frequency doubling conversion method based on the polarized crystal does not need a temperature control system, and has the advantages of simple and compact structure, low energy consumption, low cost and the like.
In order to realize quasi-phase matching, the polarization period Lambda of the nonlinear crystal is generally the coherence length l c Double, take sum frequency as an example
Wherein k is i (i ═ 1,2,3) is the laser wavevector participating in sum frequency, and in quasi-phase matching, the phase mismatch factor
Under the condition of small signal approximation, the conversion efficiency eta is
Wherein d is eff Is the effective nonlinear coefficient, L is the crystal length; when Δ k is 0, the conversion efficiency is highest, and when Δ kL is 0.886 pi, the conversion efficiency is half of the maximum value; expanding the delta k (T) according to Taylor series
When the first term in the expansion of equation (4) is zero, i.e.
The half width of the temperature can be calculated from the quadratic term
Phase mismatch and crystal temperature in nonlinear optical crystalsApproximately linear, the first order partial derivative of the amount of phase mismatch versus temperature is much larger than the second order partial derivative, and therefore T ″ BW ＞＞T′ BW (ii) a Through reasonable design of the cutting angle and the polarization period of the nonlinear optical crystal, the delta k (T) is enabled to be 0 ) Is equal to 0 and
namely, the quasi-phase matching condition is met, and the first-order partial derivative of the phase mismatch quantity to the temperature is zero, so that the frequency conversion efficiency is basically not influenced by the temperature change of the crystal;
wherein T is 0 To meet the crystal temperature at the time of quasi-phase matching, Δ T ═ T-T 0 And is and
wherein n is i (i ═ 1,2,3) is the refractive index of the laser light participating in sum frequency in the crystal; due to Δ k (T) 0 ) 0, take the first order of the above expansion, and let Δ k (t) L be 0.886 pi; the sum frequency temperature half width at this time is given:
the invention relates to a wide-temperature frequency multiplier based on quasi-phase matching, which comprises a piece of periodically polarized crystal and is cut according to a certain angle, so that the first derivative of phase mismatch quantity to temperature is zero, and the temperature width of the device is greatly improved.
The invention provides a wide-temperature frequency doubling conversion method based on quasi-phase matching, which is characterized in that the cutting angle of a traditional polarized crystal is changed, so that the nonlinear optical frequency conversion keeps higher conversion efficiency in a wider temperature range, and the temperature adaptability and stability of a nonlinear optical frequency conversion crystal device are improved. The device does not need temperature control equipment, so that the structure of the nonlinear optical frequency conversion crystal device is simpler and more compact, and meanwhile, the energy consumption of the device is reduced, the cost of the device is reduced, and the performance of the device is improved.
Drawings
FIG. 1 is a schematic diagram of a wide-temperature frequency multiplier device based on quasi-phase matching; wherein: a represents fundamental frequency light lambda 1 And (3) 1064nm, wherein Z represents the optical axis Z axis and the polarization direction of the nonlinear optical crystal, f represents the fast laser polarization direction in the nonlinear optical crystal, and Λ represents the polarization period of the nonlinear optical crystal.
FIG. 2 is a graph showing the conversion efficiency with the temperature of the PPKTP crystal when the wavelength of the double frequency wave is 1064nm laser.
FIG. 3 is a graph showing the conversion efficiency as a function of the crystal temperature when a laser having a frequency doubling wavelength of 1064nm is used in a PPMgLN crystal.
Detailed Description
The quasi-phase matching technology enables laser participating in nonlinear optical frequency conversion to meet the quasi-phase matching condition by periodically changing the polarization direction of the nonlinear optical crystal, can realize the non-critical phase matching, avoids generating space walk-off, can conveniently utilize the maximum effective nonlinear coefficient of the nonlinear optical crystal, and is widely applied to the nonlinear optical frequency conversion. However, like the birefringence phase matching, the quasi-phase matching is also affected by the temperature variation of the crystal, and generally has a small half width of the temperature peak, such as only 4.7 ℃ when a laser with a frequency doubling wavelength of 1064nm is used for a polarized potassium titanyl phosphate (PPKTP) crystal with a length of 1cm, resulting in poor environmental temperature adaptability.
To achieve quasi-phase matching, the polarization period Λ of the nonlinear crystal is typically the coherence length l c Twice as much as the amount of the first,
wherein k is i (i ═ 1,2 and 3) is a participating laser wave vector, and in quasi-phase matching, a phase mismatch factor
Conversion efficiency eta under small signal approximation condition
Wherein d is eff L is the crystal length, which is the effective nonlinear coefficient. When Δ k is 0, the conversion efficiency is highest, and when Δ kL is 0.886 pi, the conversion efficiency is half of the maximum. Expanding the delta k (T) according to Taylor series
When the first term in the expansion of equation (4) is zero, i.e.
The half width of the temperature can be calculated from the quadratic term
Wherein T is 0 To meet the crystal temperature at the time of quasi-phase matching, Δ T ═ T-T 0 And is made of
Wherein n is i (i ═ 1,2,3) is the refractive index of the laser light participating in sum frequency in the crystal. Since Δ k (t) is 0, the first order of the above expansion is taken, and Δ k (t) L is 0.886 pi. The sum frequency temperature half width at this time can be derived:
when the frequency doubling wavelength of laser in the PPKTP crystal is 1064nm, the cutting angle of the PPKTP crystal is usually (90 degrees, 0 degrees), and the phase mismatch is first order of temperatureDeflection 1.191cm -1 ℃ -1 And therefore its temperature peak half-width is only 4.7 ℃. It can be seen that when the frequency doubling wavelength of laser with 1064nm in the traditional PPKTP crystal at the cutting angle is low, the half width of the temperature peak value is low, which leads to poor temperature stability of the frequency doubling laser, and when the ambient temperature slightly deviates from the matching temperature, the power of the frequency doubling laser is sharply reduced. This feature limits its application in environments with varying temperatures, and the current solution is to control the crystal thermostatically, which however increases the system energy consumption and complexity.
The device design principle is illustrated below by taking a laser with a frequency doubling wave wavelength of 1064nm in a PPKTP crystal as an example. The type I phase matching frequency multiplication can be adopted, and the cutting angle and the polarization period of the crystal meeting the critical quasi-phase matching condition of the wide temperature range are solved. Let the crystal cutting angle be
Temperature T, phase error amount
Wherein
Respectively the refractive index of the fundamental frequency light fast light and the refractive index of the slow light. When the temperature is T 0 When 293K, the cutting angle can be obtained according to the Sellmeier equation and the thermo-optic dispersion equation of the KTP crystal
The refractive indexes of the time-base frequency light and the frequency doubling light are obtained, and the polarization period meeting the quasi-phase matching condition under the angle is obtained
The polarization period of the crystal at the temperature T is as follows due to the expansion and contraction effect
Λ(T)＝Λ 0 ·(1+α(T-T 0 )) (10)
Where α is the linear coefficient of thermal expansion. Sellmeier equation, thermo-optic dispersion equation and equation (10) of KTP crystal can be used to determine the phase mismatch amount with respect to the cutting angle
And a function of the temperature of the crystal, from which a deviation of the temperature is determined, when the first deviation is 0, i.e.
Then, the cutting angle of the corresponding crystal is obtained
Meanwhile, the effective nonlinear coefficient of the nonlinear crystal at the angle is also calculated, and the result is shown in fig. 1. As can be seen from the figure, satisfy
In the cutting direction of (a) of (b),
the angle is in the range of 62 degrees to 90 degrees, corresponding
The angle ranges from 90 to 56.8 degrees. The crystal with zero first-order partial derivative is periodically polarized to meet the quasi-phase matching condition, so that the frequency multiplication within a wide temperature range is realized.
Example 1
The nonlinear optical crystal is PPKTP crystal, the cutting angles of the crystal are (90 degrees, 56.8 degrees), and the size of the crystal is 3 multiplied by 1 multiplied by 10mm 3 The polarization period of the crystal is 170.74 μm, and the light-passing surfaces of the crystal are plated with anti-reflection films with light wave bands of 1064nm and 532 nm. And by adopting I type phase matching, in the input plane of the PPKTP crystal, the included angle between the polarization direction of the fundamental frequency light and the z-axis of the PPKTP crystal is 45 degrees.
After the PPKTP crystal parameters are determined, the phase mismatch amount of the crystal at different temperatures T is calculated and substituted into formula (3) to obtain a curve of the frequency doubling normalized conversion efficiency with the temperature change, as shown in fig. 2. As can be seen from the graph, the normalized conversion efficiency reaches a maximum of 100% at a temperature of 20 ℃, and the conversion efficiency is the lowest of 95.8% at a temperature of 140 ℃. When the temperature is changed between-100 ℃ and 140 ℃, the frequency doubling conversion efficiency is very stable, and the maximum deviation is less than 5 percent.
Example 2
The nonlinear optical crystal selects 5 mol% MgO-doped LiNbO 3 A crystal (PPMgLN) having a crystal cutting angle (θ ═ 18.6 °,
) The polarization period is lambda-5.6488 μm, and the crystal size is 3 × 1 × 10mm 3 The phase matching type is eo-o. And the light transmission surfaces of the crystals are coated with antireflection films with light wave bands of 1064nm and 532nm, and I type phase matching is adopted. After the parameters of the PPMgLN crystal are determined, the phase mismatch amount of the crystal at different crystal temperatures T is calculated and substituted into formula (3), so that a curve of normalized frequency doubling conversion efficiency changing along with the crystal temperature can be obtained, as shown in FIG. 3. As can be seen from the figure, the normalized conversion efficiency is higher than 96% in the temperature range of-150 ℃ and 100 ℃, and the conversion efficiency is higher than 99% in the temperature range of-130 ℃ to 84 ℃, the variation is smooth, and the maximum deviation is lower than 1%. Simulation results show that the temperature stability is excellent at frequency doubling in the crystal.
Claims (1)
1. A wide-temperature frequency multiplication conversion method based on quasi-phase matching is characterized in that
In order to realize quasi-phase matching, the polarization period Lambda of the nonlinear crystal is a coherent length l c Twice as much as the amount of the first,
wherein k is i (i ═ 1,2,3) is the laser wavevector participating in sum frequency, and in quasi-phase matching, the phase mismatch factor
Under the condition of small signal approximation, the conversion efficiency eta is
Wherein d is eff Is the effective nonlinear coefficient, L is the crystal length; when Δ k is 0, the conversion efficiency is highest, and when Δ kL is 0.886 pi, the conversion efficiency is half of the maximum value; Δ k (T) at a crystal temperature T 0 Is subjected to Taylor series expansion
Where T is the crystal temperature,. DELTA.k (T) and. DELTA.k (T) 0 ) Crystal temperatures of T and T, respectively 0 Amount of phase mismatch of time, Δ T ═ T-T 0 . When the first term in the expansion of equation (4) is zero, i.e.
The half width of the temperature is calculated from the quadratic term
The phase mismatch quantity in the nonlinear optical crystal is approximately linear with the crystal temperature, the second order partial derivative of the phase mismatch quantity to the temperature is much larger than the first order partial derivative, therefore T ″ BW ＞＞T′ BW (ii) a Combining the thermo-optic dispersion equation of the crystal and the Sellmeier equation to make Δ k (T) 0 ) Is equal to 0 and
the cutting angle and polarization of the nonlinear optical crystal can be solved so that the quasi-phase matching condition is satisfied and the first-order partial derivative of the phase mismatch amount to the temperature is zeroA period;
wherein T is 0 To meet the crystal temperature at the time of quasi-phase matching, Δ T ═ T-T 0 And is and
wherein n is i (i ═ 1,2,3) is the refractive index of the participating laser light in the crystal; due to Δ k (T) 0 ) 0, take the first order of the above expansion, and let Δ k (t) L be 0.886 pi; the temperature half width at this time is given as:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210381059.4A CN114967274A (en) | 2022-04-12 | 2022-04-12 | Wide-temperature frequency multiplication conversion method based on quasi-phase matching |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210381059.4A CN114967274A (en) | 2022-04-12 | 2022-04-12 | Wide-temperature frequency multiplication conversion method based on quasi-phase matching |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN114967274A true CN114967274A (en) | 2022-08-30 |
Family
ID=82976569
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210381059.4A Pending CN114967274A (en) | 2022-04-12 | 2022-04-12 | Wide-temperature frequency multiplication conversion method based on quasi-phase matching |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114967274A (en) |
-
2022
- 2022-04-12 CN CN202210381059.4A patent/CN114967274A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5787102A (en) | Light generating device and method using a periodically structured non-linear material and orthogonal optical interaction | |
| Heismann et al. | Wavelength-tunable electrooptic polarization conversion in birefringent waveguides | |
| McGowan et al. | Femtosecond optical parametric oscillator based on periodically poled lithium niobate | |
| CN102929071A (en) | Single-frequency terahertz source generated by using single-frequency laser as nonlinear difference frequency | |
| WO1993026066A1 (en) | Nonlinear optical frequency converter | |
| Kobashi et al. | Broadband optical vortex generation from patterned cholesteric liquid crystals | |
| CN113540933B (en) | Intermediate infrared parametric laser based on synchronous double-optical parametric process | |
| Zhu et al. | Wide-range tunable wavelength filter in periodically poled lithium niobate | |
| CN114967274A (en) | Wide-temperature frequency multiplication conversion method based on quasi-phase matching | |
| CN115632300A (en) | Method for generating tunable narrow-band laser | |
| CN103001111A (en) | Terahertz source generated based on nonlinear difference frequency of fiber lasers | |
| Cui et al. | 70-W average-power doubly resonant optical parametric oscillator at 2 μm with single KTP | |
| CN102044833A (en) | Method for setting broadband continuously-tunable lasers and implementation device thereof | |
| CN111755943B (en) | Optical parametric oscillator based on pulse laser pumping and working method | |
| Yao et al. | Frequency conversion dynamics of vector modulation instability in normal-dispersion high-birefringence fibers | |
| Liu et al. | Three-crystal method for thermally induced phase mismatch compensation in second-harmonic generation | |
| Padgett et al. | Mode selection in doubly-resonant optical parametric oscillators | |
| CN114371584A (en) | Nonlinear optical frequency conversion crystal device capable of expanding temperature adaptation range | |
| Chen et al. | Fourth harmonic generation based on miniaturized tunable bow-tie resonators | |
| CN114371583A (en) | Femtosecond laser ultra-wideband high-efficiency frequency multiplier based on single nonlinear crystal | |
| Liu et al. | Temperature-insensitive frequency conversion achieved by phase-matching outside principal planes and thermally induced phase-mismatch compensation | |
| JP2899345B2 (en) | Optical device | |
| CN114706254A (en) | Broadband frequency multiplication method and system for dense light wave multiplexing system | |
| Zhao et al. | An efficient, compact intra-cavity continuous-wave mid-infrared SRO with a narrow line width | |
| Wang et al. | High-repetition-rate narrow pulse width mid-infrared optical parametric oscillator based on PPMgLN crystal |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |