CN115826379A - LiNH 4 SO 4 Application of crystal in deep ultraviolet quasi-phase matching optical device and preparation method thereof - Google Patents
LiNH 4 SO 4 Application of crystal in deep ultraviolet quasi-phase matching optical device and preparation method thereof Download PDFInfo
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- CN115826379A CN115826379A CN202211435541.8A CN202211435541A CN115826379A CN 115826379 A CN115826379 A CN 115826379A CN 202211435541 A CN202211435541 A CN 202211435541A CN 115826379 A CN115826379 A CN 115826379A
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Abstract
The invention relates to LiNH 4 SO 4 A method for preparing an optical device of a quasi-phase matching crystal and application thereof. LiNH 4 SO 4 The crystal is applied to the preparation of deep ultraviolet quasi-phase matching optical devices. LiNH 4 SO 4 The quasi-phase matching crystal has the advantages of short ultraviolet absorption cut-off edge, moderate nonlinear optical effect, low refractive index dispersion, stable physical and chemical properties, good mechanical properties and the like, so that the quasi-phase matching crystal can be applied to deep ultraviolet quasi-phase matching optical devices.
Description
Technical Field
The present invention relates to LiNH 4 SO 4 The application of the crystal in a deep ultraviolet quasi-phase matching optical device and a preparation method thereof.
Technical Field
The nonlinear optical effect of a crystal refers to an effect that: when a laser beam with a certain polarization direction passes through a nonlinear optical crystal in a certain direction, the frequency of the beam changes. Crystals with nonlinear optical effects are referred to as nonlinear optical crystals. By using the nonlinear optical effect of the crystal, nonlinear optical devices such as a second harmonic generator, an upper frequency converter, a lower frequency converter, an optical parametric oscillator and the like can be manufactured. In the second-order nonlinear process, the difference in propagation speed in the crystal is caused by the difference in wavelength between the fundamental frequency light and the frequency doubling light, so that energy repeatedly flows between the fundamental frequency light and the frequency doubling light, and effective enhancement cannot be realized, which is called phase mismatch.
At present, a nonlinear optical crystal applied to an ultraviolet band is mainly based on a birefringence principle, so that refractive indexes of fundamental frequency light and frequency doubling light are equal in a certain direction, and thus phase mismatch Δ k =0 is called birefringence phase matching. However, the birefringence phase matching has a disadvantage that the requirement for birefringence is high, and only the nonlinear optical coefficient in a specific direction can be utilized. The quasi-phase matching is characterized in that a nonlinear coefficient periodic reversal structure is constructed in a nonlinear optical crystal by taking a coherence length as a period, so that energy continuously flows from fundamental frequency light to frequency doubling light after the phase of the frequency doubling light is reversed by pi after passing through one coherence length, and the quasi-phase matching has the advantages of low requirement on birefringence, richer supplied reciprocal lattice vectors and the like compared with the birefringent phase matching.
The existing quasi-phase matching crystal mainly comprises BaMgF 4 、LiNbO 3 、LiTaO 3 、KTiOPO 4 、LaBGeO 5 Etc., wherein, liNbO 3 、LiTaO 3 、KTiOPO 4 When the cut-off edges of the crystals are all above 300nm, the output of the deep ultraviolet wave band can not be realized, and LBGO and BaMgF 4 Because the refractive index dispersion of the crystal is large, the polarization period required by the crystal to realize quasi-phase matching output in a deep ultraviolet band is very small, and the processing difficulty is very high. Therefore, the search for deep ultraviolet quasi-phase-matching crystals with excellent combination properties is still urgent and necessary.
Disclosure of Invention
The object of the present invention is to provide LiNH 4 SO 4 The application of the crystal in a deep ultraviolet quasi-phase matching optical device and a preparation method thereof. LiNH 4 SO 4 The quasi-phase-matched crystal has short ultravioletThe absorption cut-off edge, moderate nonlinear optical effect, low refractive index dispersion, stable physical and chemical properties, good mechanical properties and the like, so that the optical fiber can be applied to a deep ultraviolet quasi-phase matching optical device.
The technical scheme of the invention is as follows:
LiNH 4 SO 4 the crystal is applied to a deep ultraviolet quasi-phase matching optical device.
A quasi-phase-matching optical device is composed of LiNH 4 SO 4 And (5) preparing crystals.
The preparation method of the quasi-phase matching optical device comprises the following steps:
(1) Reacting LiNH 4 SO 4 Crystal orientation perpendicular to LiNH 4 SO 4 Cutting the crystal b direction into thin sheets, and making the thin sheets perpendicular to the LiNH 4 SO 4 Polishing two surfaces in the direction of the crystal b, then uniformly coating silver paste on the two surfaces, and then putting the two surfaces into a sample box for polarization;
(2) Then heating the crystal obtained in the step (1) and a sample box for polarization to 140-150 ℃, applying an external voltage of 4-4.5kV, and keeping for 10-15min to complete single domain of the wafer;
(3) Then removing silver paste on the crystal surface after the step (2), plating a metal film with consistent thickness and material on the two surfaces, and then plating the LiNH on the two surfaces 4 SO 4 Photoetching one surface of the crystal by the coherent length obtained by calculating the refractive index dispersion equation of the crystal to prepare a corresponding electrode structure and form a grating electrode required by polarization;
(4) And applying a square wave electric field to the wafer for multiple times by using a high-voltage pulse power supply to complete periodic polarization, and finally removing the metal film on the surface of the wafer to obtain the quasi-phase matching optical device.
Preferably, the metal film is Cr or Al with the thickness of 80-120 nm.
Preferably, after polishing in step (1), said sheet is oriented along said LiNH 4 SO 4 The thickness in the direction of crystal b is 1-1.5mm.
Compared with the prior art, the invention has the following beneficial effects:
(1)LiNH 4 SO 4 the quasi-phase matching crystal has the advantages of short ultraviolet absorption cut-off edge, moderate nonlinear optical effect, low refractive index dispersion, stable physical and chemical properties, good mechanical properties and the like;
(2) The quasi-phase matching device manufactured by the quasi-phase matching crystal can be used in a plurality of high-tech fields, such as laser photoetching, micromachining, photochemistry, high-resolution spectral analysis and the like.
Drawings
FIG. 1 is a schematic representation of a LiNH reaction 4 SO 4 A working principle diagram of a deep ultraviolet quasi-phase matching optical device made of crystal, wherein 1 is laser, 2 is incident laser beam, and 3 is LiNH 4 SO 4 The manufactured deep ultraviolet quasi-phase matching optical device is provided with 4 the generated laser beam and 5 the optical filter.
Detailed Description
The invention is further described below with reference to the following examples and the accompanying drawings. It will be understood by those skilled in the art that the following examples are not intended to limit the scope of the present invention, and that any modifications and variations based on the present invention are within the scope of the present invention.
Examples 1 to 6 relate to LiNH 4 SO 4 And (5) preparing a quasi-phase matching device.
Example 1
LiNH is obtained by electric field polarization method 4 SO 4 The quasi-phase matching device specifically operates according to the following steps:
a) Reacting LiNH 4 SO 4 Cutting the crystal in the direction vertical to the direction b, polishing and processing the crystal into a wafer with the thickness of 1mm, uniformly coating silver paste on the upper surface and the lower surface of the wafer, and putting the wafer into a sample box for polarization;
b) And (3) heating the wafer in the step (1) to 150 ℃, applying an external voltage of 4kV, and keeping for 15min to finish the single domain of the wafer.
c) Removing silver paste on the surface of the wafer, and marking the positive and negative surfaces: and the + b surface and the-b surface of the wafer are plated, the metal used for plating is Cr, al or other metal materials, and the thickness is 100nm. And photoetching the + b surface to prepare an electrode structure with the period of 6.8 mu m and form a grating electrode required by polarization.
d) Plating a metal film with the same thickness as the + b surface material on the-b surface of the wafer as a negative electrode, applying a square wave electric field to the wafer for a certain number of times by using a high-voltage pulse power supply to complete periodic polarization, and removing the metal electrode on the surface of the wafer. Obtaining the deep ultraviolet quasi-phase matching device with the conversion wavelength of 532nm to 266 nm.
Example 2
LiNH is obtained by electric field polarization method 4 SO 4 The quasi-phase matching device specifically operates according to the following steps:
a) Reacting LiNH 4 SO 4 Cutting the crystal in the direction vertical to the direction b, polishing and processing the crystal into a wafer with the thickness of 1mm, uniformly coating silver paste on the upper surface and the lower surface of the wafer, and putting the wafer into a sample box for polarization;
b) And (3) heating the wafer in the step (1) to 140 ℃, applying an external voltage of 4.5kV, and keeping for 10min to finish the single domain formation of the wafer.
c) Removing silver paste on the surface of the wafer, and marking the positive and negative surfaces: and the + b surface and the-b surface of the wafer are plated, the metal used for plating is Cr, al or other metal materials, and the thickness is 100nm. And photoetching the + b surface to prepare an electrode structure with the period of 1.4 mu m and form a grating electrode required by polarization.
d) Plating a metal film with the same thickness as the + b surface material on the-b surface of the wafer as a negative electrode, applying a square wave electric field to the wafer for a certain number of times by using a high-voltage pulse power supply to complete periodic polarization, and removing the metal electrode on the surface of the wafer. The deep ultraviolet quasi-phase matching device with the conversion wavelength of 354.6nm to 177.3nm is obtained.
Example 3
LiNH is obtained by electric field polarization method 4 SO 4 The quasi-phase matching device is specifically operated according to the following steps:
a) Reacting LiNH 4 SO 4 Cutting the crystal in the direction vertical to the direction b, polishing and processing the crystal into a wafer with the thickness of 1mm, uniformly coating silver paste on the upper surface and the lower surface of the wafer, and putting the wafer into a sample box for polarization;
b) And (3) heating the wafer in the step (1) to 145 ℃, applying an external voltage of 4.2kV, and keeping for 12min to finish the single domain of the wafer.
c) Removing silver paste on the surface of the wafer, and marking the positive and negative surfaces: and the + b surface and the-b surface of the wafer are coated, the metal used for coating is Cr, al or other metal materials, and the thickness is 80nm. And photoetching the + b surface to prepare an electrode structure with the period of 6.8 mu m and form a grating electrode required by polarization.
d) Plating a metal film with the same thickness as the + b surface material on the-b surface of the wafer as a negative electrode, applying a square wave electric field to the wafer for a certain number of times by using a high-voltage pulse power supply to complete periodic polarization, and removing the metal electrode on the surface of the wafer. Obtaining the deep ultraviolet quasi-phase matching device with the conversion wavelength of 532nm to 266 nm.
Example 4
LiNH is obtained by electric field polarization method 4 SO 4 The quasi-phase matching device is specifically operated according to the following steps:
a) Reacting LiNH 4 SO 4 Cutting the crystal in the direction vertical to the direction b, polishing the crystal into a wafer with the thickness of 1mm, uniformly coating silver paste on the upper surface and the lower surface of the wafer, and putting the wafer into a sample box for polarization;
b) And (3) heating the wafer in the step (1) to 150 ℃, applying an external voltage of 4kV, and keeping for 15min to finish the single domain of the wafer.
c) Removing silver paste on the surface of the wafer, and marking the positive and negative surfaces: and the + b surface and the-b surface of the wafer are plated, the metal used for plating is Cr, al or other metal materials, and the thickness is 80nm. And photoetching the + b surface to prepare an electrode structure with the period of 1.4 mu m and form a grating electrode required by polarization.
d) Plating a metal film with the same thickness as the + b surface material on the-b surface of the wafer as a negative electrode, applying a square wave electric field to the wafer for a certain number of times by using a high-voltage pulse power supply to complete periodic polarization, and removing the metal electrode on the surface of the wafer. The deep ultraviolet quasi-phase matching device with the conversion wavelength of 354.6nm to 177.3nm is obtained.
Example 5
LiNH is obtained by electric field polarization method 4 SO 4 A quasi-phase-matching device, which is,the specific operation is carried out according to the following steps:
a) Reacting LiNH 4 SO 4 Cutting the crystal in the direction vertical to the direction b, polishing and processing the crystal into a wafer with the thickness of 1mm, uniformly coating silver paste on the upper surface and the lower surface of the wafer, and putting the wafer into a sample box for polarization;
b) And (3) heating the wafer in the step (1) to 150 ℃, applying an external voltage of 4kV, and keeping for 15min to finish the single domain of the wafer.
c) Removing silver paste on the surface of the wafer, and marking the positive and negative surfaces: and the + b surface and the-b surface of the wafer are plated, the metal used for plating is Cr, al or other metal materials, and the thickness is 100nm. And photoetching the + b surface to prepare an electrode structure with the period of 2.3 mu m and form a grating electrode required by polarization.
d) Plating a metal film with the same thickness as the + b surface material on the-b surface of the wafer as a negative electrode, applying a square wave electric field to the wafer for a certain number of times by using a high-voltage pulse power supply to complete periodic polarization, and removing the metal electrode on the surface of the wafer. Obtaining the deep ultraviolet quasi-phase matching device with the conversion wavelength of 400nm to 200 nm.
Example 6
LiNH obtained by electric field polarization 4 SO 4 The quasi-phase matching device is specifically operated according to the following steps:
a) Reacting LiNH 4 SO 4 Cutting the crystal in the direction vertical to the direction b, polishing and processing the crystal into a wafer with the thickness of 1mm, uniformly coating silver paste on the upper surface and the lower surface of the wafer, and putting the wafer into a sample box for polarization;
b) And (3) heating the wafer in the step (1) to 150 ℃, applying an external voltage of 4kV, and keeping for 15min to finish the single domain of the wafer.
c) Removing silver paste on the surface of the wafer, and marking the positive and negative surfaces: and the + b surface and the-b surface of the wafer are coated, the metal used for coating is Cr, al or other metal materials, and the thickness is 80nm. And photoetching the + b surface to prepare an electrode structure with the period of 2.3 mu m and form a grating electrode required by polarization.
d) Plating a metal film with the same thickness as the + b surface material on the-b surface of the wafer as a negative electrode, applying a square wave electric field to the wafer for a certain number of times by using a high-voltage pulse power supply to complete periodic polarization, and removing the metal electrode on the surface of the wafer. Obtaining the deep ultraviolet quasi-phase matching device with the conversion wavelength of 400nm to 200 nm.
FIG. 1 is a simplified illustration of a nonlinear optical device fabricated using LiNH4SO4 crystals in accordance with the present invention. A beam 2 emitted from a laser 1 is incident on a periodically polarized LiNH 4 SO 4 The crystal 3, the produced emergent beam 4 passes through the filter 5, thereby obtaining the required laser beam. The nonlinear optical laser can be a frequency doubling generator or an upper and a lower frequency converter or an optical parametric oscillator, etc.
The above embodiments are merely detailed explanations of the technical solutions of the present invention, and the present invention is not limited to the above embodiments, and it should be understood that all modifications and substitutions based on the above principles and spirit of the present invention should be within the protection scope of the present invention.
Claims (5)
1.LiNH 4 SO 4 The crystal is applied to the preparation of deep ultraviolet quasi-phase matching optical devices.
2. A deep ultraviolet quasi-phase matching optical device, characterized by: the LiNH of claim 1 4 SO 4 And (5) preparing crystals.
3. The method for manufacturing a deep ultraviolet quasi-phase-matching optical device according to claim 2, comprising the steps of:
(1) Reacting LiNH 4 SO 4 Crystal orientation perpendicular to LiNH 4 SO 4 Cutting the crystal b direction into thin sheets, and making the thin sheets perpendicular to the LiNH 4 SO 4 Polishing two surfaces in the direction of the crystal b, then uniformly coating silver paste on the two surfaces, and then putting the two surfaces into a sample box for polarization;
(2) Then heating the crystal obtained in the step (1) and a sample box for polarization to 140-150 ℃, applying an external voltage of 4-4.5kV, and keeping for 10-15min to complete single domain of the wafer;
(3) Then will get the stepRemoving silver paste on the crystal surface in the step (2), plating metal films with consistent thickness and material on the two surfaces, and then plating the LiNH 4 SO 4 Photoetching one surface of the crystal by the coherent length obtained by calculating the refractive index dispersion equation of the crystal to prepare a corresponding electrode structure and form a grating electrode required by polarization;
(4) And applying a square wave electric field to the wafer for multiple times by using a high-voltage pulse power supply to complete periodic polarization, and finally removing the metal film on the surface of the wafer to obtain the quasi-phase matching optical device.
4. The method of manufacturing a deep ultraviolet quasi-phase matching optical device according to claim 3, wherein: the metal film is Cr or Al with the thickness of 80-120 nm.
5. The method of manufacturing a deep ultraviolet quasi-phase matching optical device according to claim 3, wherein: after polishing in step (1), the sheet is polished along the LiNH 4 SO 4 The thickness in the direction of crystal b is 1-1.5mm.
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