KR20090103299A - Optical device using resonant waveguide and method for operating the same - Google Patents

Abstract

PURPOSE: An optical device using a resonant optical waveguide and an operation method thereof are provided to improve a device response property by reducing an absorption loss. CONSTITUTION: An optical device includes an optical delivering part and an optical waveguide. The optical delivering part(1) propagates a signal beam(4). The optical waveguide is optically connected to the optical delivering part, and receives the signal beam propagated from the optical delivering part with a waveguide mode angle. In the optical waveguide, a pump beam is received to the same point as the point in which the signal beam is received. A wavelength of the signal beam and a wavelength of the pump beam are different. The waveguide mode angle of the optical waveguide(3) is determined by the pump beam(7).

Description

Optical device using resonant optical waveguide and its operation method {OPTICAL DEVICE USING RESONANT WAVEGUIDE AND METHOD FOR OPERATING THE SAME}

The present invention relates to an optical device using a resonant optical waveguide and a method of operating the same. Specifically, the optical nonlinearity enhancing effect inherent to a material such as a nanocomposite is maximized while the light absorption loss and device performance accompanying the same are reduced. An optical device configured to perform light modulation and light switching while minimizing and a method of operating the same.

In order to implement an optical switching device operated by pure optical means, it is necessary to develop a material that is sensitive to light and has a large change in refractive index according to light intensity. As such a material, a material exhibiting a nonlinear refractive index phenomenon in which the refractive index of the medium is changed by changing the intensity of incident light, which is one of the third nonlinear optical effects, can be used.

In particular, among materials in which tertiary nonlinear optical phenomena are expressed by resonance, a composite material in which metal and semiconductor nanoparticles are dispersed in a dielectric matrix has a dielectric confinement effect and a quantum confinement effect, respectively. Due to the resonance characteristic expressed by), the change of the refractive index is large, attracting attention. In addition, these composite materials have a fast reaction speed with respect to light, and are easy to control the resonant wavelength depending on the size and shape of the particles and the selection of the constituent material system.

On the other hand, an optical switch element based on the optical properties inherent in such a material includes a Mach-Zehnder Interferometer type switching element that forms an interferometer using a phase shift effect through the interaction of a signal beam and a material. .

The Mach-Zehnder interferometer switching element is divided into two beams by a waveguide type splitter, propagates through different paths along neighboring optical waveguides, and then recombines with each other. It is a device that implements optical signal switching by interference effect. That is, when the phases of the two beams coincide with each other at the coupling end, constructive interference occurs when the phases of the two beams differ by 180 degrees.

In this case, the phase difference between the two beams is induced by changing the relative refractive index of one arm constituting the interferometer, the magnitude of which is proportional to the nonlinear optical coefficient of the material including the photo-thermal reaction and the waveguide length at which the reaction occurs. Done. It is desirable to increase the overall reaction length in order to achieve a sufficient degree of phase shift while lowering the energy required for switching.

However, when the resonant nanocomposite is used, the light absorption at the resonant wavelength at which the optical nonlinearity is the highest due to the nature of the resonance characteristic is very large. Therefore, it is difficult to constitute the entire waveguide with these materials. Although there is a method of constructing an interferometer by replacing and inserting only a local region on the waveguide with a nanocomposite, there is a problem in that the manufacturing process is difficult and the loss of the signal beam is severe due to the refractive index mismatch and the interface nonuniformity at the interface between different materials.

As described above, the above-described prior art limits the operating wavelength of the device to the resonant wavelength band where the nonlinearity is maximized, so that the inherent light absorption loss of the device is difficult to be avoided when the resonant nanocomposite material is applied to the optical switch device. Has

U.S. Patent No. 7,181,114, entitled "Waveguide Type Optical Device Using Giant Tertiary Nonlinear Optical Material and Its Operation Method" to solve this problem, uses a heterogeneous waveguide structure by separating a wavelength band of a signal beam and a pump beam. Disclosed is a cross-modulation switching device.

The waveguide of the Mach-Zehnder interferometer is formed of a nanocomposite material, but the light of non-resonant wavelength in the near infrared region with low light absorption is guided along the interferometer waveguide with a signal beam. In addition, the pump beam of the resonant wavelength band propagated through an external waveguide formed of an optically transparent material to the light of the resonant wavelength is coupled to one arm of the interferometer, thereby inducing a change in refractive index of the nanocomposite material and consequently the signal beam Implements the switching operation.

However, referring to FIGS. 1 and 2, it can be seen that even in this case, deterioration of the device performance due to light absorption of the nanocomposite itself is inevitable. 1 is a graph showing the light absorption characteristics of a nanocomposite thin film, and shows the results measured for a thin film in which gold nanoparticles were dispersed in a SiO ₂ matrix with a volume fraction of 1%. Light absorption peaks due to surface plasmon resonance (SPR) of gold nanoparticles occur at about 530 nm wavelength, and the light absorption decreases toward the longer wavelength.

However, even when using a signal beam in the near infrared wavelength band far from the surface plasmon resonance wavelength, it still has several ten times higher light absorption than conventional transparent dielectric optical waveguide materials in which metal or semiconductor nanoparticles are not dispersed. Indicates.

On the other hand, Figure 2 is a graph showing the intensity change according to the waveguide distance of the waveguide beam in the nanocomposite thin film. The graphs 200 and 201 shown in FIG. 2 show that the Au: SiO ₂ nanocomposite thin film was adjusted to 1% (200) and 5% (201) volume fractions of gold nanoparticles, respectively. _The result of guiding the waveguide of 1550 nm wavelength with respect to the slab-type optical waveguide deposited on _two substrates is shown.

As shown in FIG. 2, even when light having a non-resonant wavelength of 1550 nm is used, the intensity of the waveguide beam is rapidly attenuated according to the waveguide distance due to light absorption of the nanocomposite itself. When the volume fraction of the gold nanoparticles is 1%, the waveguide distance having a size of 1 / e of the initial incident beam intensity is 108 µm, and when the volume fraction is 5%, the waveguide distance is only 34 µm. Considering that the length of the integrated optical waveguide device is several mm to several cm, it can be seen that the application to the actual device is not easy and the performance degradation of the device due to light absorption loss is inevitable.

Since the light absorption in the nanocomposite material is linearly proportional to the volume fraction of the dispersed nanoparticles, it is possible to ensure sufficient light transmittance in the communication wavelength band when the volume fraction is reduced to an extremely small amount. However, since the nonlinear optical coefficient at the resonant wavelength also decreases in proportion to the volume fraction of the nanoparticles, the energy for optical switching is greatly increased, which is undesirable.

The present invention for solving the problems of the prior art, using the optical nonlinearity enhancement effect inherent in the nanocomposite material to the maximum while using the optical waveguide using a resonant nanocomposite optical waveguide reduced optical absorption loss and device degradation An object of the present invention is to provide an element and a method of operating the same.

An optical device according to an aspect of the present invention for achieving the above object, the light transmission unit propagates the signal beam; And an optical waveguide optically connected to the light transmitting unit, the signal beam propagated from the light transmitting unit propagating at a waveguide mode angle, and a pump beam incident on the same point as the point at which the signal beam is incident. The wavelength of the signal beam and the wavelength of the pump beam may be different from each other, and the waveguide mode angle of the optical waveguide may be determined by the pump beam.

According to another aspect of the present invention, an optical device includes: a light transmission unit through which a signal beam and a pump beam are propagated; And an optical waveguide optically connected to the light transmitting unit, wherein the pump beam and the signal beam propagated at the waveguide mode angle from the light transmitting unit are incident at the same position, the wavelength of the signal beam and the pump beam. Are different from each other, and the waveguide mode angle of the optical waveguide may be determined by the pump beam.

According to still another aspect of the present invention, there is provided a method of operating an optical device, the method comprising: injecting the signal beam to the light transmitting part for incident on the optical waveguide of the optical device configured as described above at a waveguide mode angle; And injecting the pump beam to determine the waveguide mode angle of the optical waveguide at the same point as the point where the signal beam is incident on the optical waveguide.

By using the optical device and the method of operating the same according to an embodiment of the present invention, the optical switch operation method that depends on the refractive index change of the nonlinear optical material itself is applied, so the excellent nonlinear optical characteristics of the resonant nanocomposite are maximized while There is an advantage in that optical modulation and optical switching with improved device response characteristics by reducing the accompanying absorption loss.

1 is a graph showing the light absorption spectrum of a nanocomposite thin film.

Figure 2 is a graph showing the change in intensity of the waveguide beam with the waveguide distance in the nanocomposite thin film.

3 is a longitudinal sectional view schematically showing an optical device according to a first embodiment of the present invention;

FIG. 4 is a graph showing a reflectance curve versus an incident angle of a signal beam according to a change in refractive index of an optical waveguide in an optical device according to a first exemplary embodiment of the present invention.

FIG. 5 is another graph illustrating a reflectance curve versus an incident angle of a signal beam according to a change in refractive index of an optical waveguide in an optical device according to a first exemplary embodiment of the present invention.

FIG. 6 is a graph illustrating reflectance curves of wavelengths of signal beams according to refractive index changes of an optical waveguide in an optical device according to a first exemplary embodiment of the present invention.

FIG. 7 is a graph illustrating a reflectance curve versus an incident angle of a signal beam according to the intensity of a pump beam in an optical device according to a first exemplary embodiment of the present invention.

8 is a graph showing the time response characteristics of the optical device according to the flashing of the pump beam in the optical device according to the first embodiment of the present invention.

9 is a graph showing the response characteristics when irradiating a single pulse pump beam to the optical device according to the first embodiment of the present invention.

10 is a graph showing the response characteristics of the optical device according to the first embodiment of the present invention when using a coupling layer composed of different materials.

FIG. 11 is yet another graph showing the response characteristic when irradiating a single pulsed pump beam to an optical device according to the first embodiment of the present invention. FIG.

12 is a longitudinal sectional view schematically showing an optical device according to a second embodiment of the present invention;

13 is a longitudinal sectional view schematically showing an optical device according to a third embodiment of the present invention;

14 is a longitudinal sectional view schematically showing an optical device according to a fourth embodiment of the present invention;

15 is a longitudinal sectional view schematically showing an optical device according to a fifth embodiment of the present invention;

Hereinafter, with reference to the accompanying drawings will be described in detail embodiments of the present invention.

3 is a longitudinal sectional view schematically showing an optical device according to a first embodiment of the present invention. As shown in FIG. 3, the optical device according to the embodiment includes a light transmitting unit 1 and 2 and an optical waveguide 3. In the embodiment shown in FIG. 1, the light transmitting portion is composed of a prism 1 and a coupling layer 2. The coupling layer 2 is optically connected to one side of the prism 1, and the optical waveguide 3 is optically connected to the coupling layer 2.

The prism 1 is optically transparent at the operating wavelength such that the signal beam 4 incident on one surface of the prism 1 propagates in the prism 1. The signal beam 4 may be formed by using light of a wavelength band having a small absorption of light by the optical waveguide 3 from the resonance wavelength of the optical waveguide 3. In one embodiment of the invention, the signal beam 4 is formed using light having a wavelength of 700 nm to 1800 nm.

The coupling layer 2 is optically connected between the prism 1 and the optical waveguide 3, and when the signal beam 4 is incident at a predetermined waveguide mode angle, the coupling layer 2 receives the signal beam 4 from the optical waveguide 3. Coupling to The signal beam 4 incident at an angle other than the waveguide mode angle is totally reflected at the coupling layer 2. For total reflection, the coupling layer 2 may be made of a material having a refractive index smaller than that of the prism 1 and that of the optical waveguide 3. In one embodiment of the invention, the coupling layer 2 may consist of MgF ₂ .

The optical waveguide 3 is optically connected to the coupling layer 2, to which the signal beam 4 incident at the waveguide mode angle is coupled. In addition, the pump beam 7 is incident at the point where the signal beam 4 of the optical waveguide 3 is coupled to control the refractive index of the optical waveguide 3. In order for the refractive index to be controlled by the pump beam 7, the optical waveguide 3 may be comprised of, for example, a nanocomposite material.

Nanocomposites are composed of metal or semiconductor nanoparticles dispersed in a dielectric or semiconductor matrix. As the base material, any material that is optically transparent in the operating wavelength band can be used without limitation, such as organic materials, inorganic materials, mixtures and composites thereof. In one embodiment of the present invention, the matrix material is a material satisfying the condition of the following equation (1) in the operating wavelength band.

In Equation 1, a is the linear light absorption of the known phase material, and n represents the refractive index of the known phase material at the corresponding operating wavelength.

As a material satisfying the condition of Equation 1, SiO ₂ , TiO ₂ , ZrO ₂ , HfO ₂ , Al ₂ O ₃ , CdO, ZnO, In ₂ O ₃ , SnO ₂ , Ga ₂ O ₃ , Y ₂ O ₃ , BeO, MgO, WO ₃ , V ₂ O ₃ , BaTiO ₃ and PbTiO ₃ Oxides, such as Si ₃ N ₄ , Al ₃ N ₄ Such as nitrides, InP, GaP, etc. of printed matter, ZnS, As ₂ S ₃ and so on of _{sulfide, MgF 2, CaF 2, NaF} , BaF 2, PbF 2, LiF, LaF such as fluoride, ZnSe, such as selenide and their Inorganic materials composed of mixtures, organic materials such as polycarbonate or polymethyl methacrylate (PMMA), and mixtures and composites thereof may be used.

In the case of nanocomposite materials, the metal particles are Au, Ag, Cu, Al, In, Sn, Pb, Sb, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Ru, Rh, Pd , Transition metals such as Ta, W and Pt and alloys thereof. Meanwhile, the semiconductor particles may be made of a material selected from semiconductors such as Si, Ge, CdS, CdSe, CdTe, CuBr, AgBr, CuCl, InP, GaP, GaAs and InAs, and solid solutions and compounds therebetween.

In addition, in the above, as an example of a material exhibiting a large tertiary nonlinear optical phenomenon, a nanocomposite material in which metal or semiconductor nanoparticles absorbed in a wavelength range of a pump beam is dispersed on a dielectric or a semiconductor substrate is used as an example. This greatly occurs and can be applied to all materials such as transition metal oxides, ferroelectric oxides, or polymer materials in which the wavelength region of the signal beam and the wavelength region of the signal beam in which the third nonlinear phenomenon is largely occur.

Hereinafter, the operation of the optical device according to the first embodiment of the present invention described above with reference to FIGS. 3 to 11 will be described.

The signal beam 4 propagating in the prism 1 reaches the interface between the prism 1 and the coupling layer 2. At this time, since the refractive index of the coupling layer 2 is smaller than that of the prism 1 and the optical waveguide 3, the signal beam 4 is totally reflected at the interface between the prism 1 and the coupling layer 2 above a certain critical angle. Causes

The totally reflected signal beam 4 is again emitted to the opposite side of the prism 1. However, at a certain angle of incidence, called the waveguide mode angle, the signal beam 4 propagates within the coupling layer 2 and is coupled to the optical waveguide 3. The signal beam 4 coupled to the optical waveguide 3 becomes a waveguide beam 6 and is mode constrained in the optical waveguide 3. The waveguide mode angle described above is determined by the refractive index and the thickness of the optical waveguide 3. Therefore, when the refractive index of the optical waveguide 3 changes, the value of the waveguide mode angle at which the signal beam 4 is coupled to the optical waveguide is also different.

Meanwhile, in one embodiment of the present invention, the optical waveguide 3 includes nanocomposites exhibiting a third order nonlinear optical effect. Therefore, when the pump beam 7 corresponding to the resonant wavelength of the nanocomposite is incident on the same point on the bottom of the prism coupled to the optical waveguide 3, the mode-constrained signal beam 6 feels. The refractive index change of the optical waveguide 3 is induced. Therefore, the reflectivity curve changes according to the intensity of the pump beam 7, thereby enabling light modulation and light switching using the same.

4 and 5 are graphs showing theoretically calculated reflectances of optical elements according to refractive index changes of the optical waveguide 3 for each incident angle θ _p . The reflectivity of the optical element is measured by the intensity of the signal beam 5 emitted from the prism 1 by causing total reflection at the interface between the prism 1 and the coupling layer 2. 4 and 5, at a specific angle of incidence where the signal beam 4 is coupled to the waveguide beam 6 corresponding to the waveguide mode angle of the optical waveguide 3, a sharp dip in the reflectivity curve ) Is formed.

The graphs of FIGS. 4 and 5 show a photon using an SF10 prism (1), a 700 nm thick MgF ₂ coupling layer (2), and a 3 μm thick Au (1% by volume): SiO ₂ nanocomposite optical waveguide (3). This is the result of calculating the reflectivity of the ruler. In this case, the refractive index of the prism 1 corresponds to 1.69, and the refractive index of the coupling layer 2 corresponds to 1.37. For example, assuming that the complex refractive index of the optical waveguide 3 is 1.5 + i0.0004 when the wavelength of the signal beam 4 is 1550 nm, FIGS. 4 and 5 show the real part of the complex refractive index of the optical waveguide 3 and The change in reflectivity according to the change in the imaginary part is shown for each incident angle.

Each of the graphs 400, 401, 402, 403 in FIG. 4 shows a graph when the change in the real part of the complex refractive index of the optical waveguide 3 is 0, 0.001, 0.005 and 0.01, respectively. As shown, when the real part of the refractive index changes, the angle of the waveguide mode in which the dip is formed in the reflectivity changes according to the degree of change in the refractive index.

On the other hand, each of the graphs 500, 501, 502, and 503 in FIG. 5 shows graphs when the imaginary part of the complex refractive index of the optical waveguide 3 is 0, 0.001, 0.005 and 0.01, respectively. As shown, when the imaginary part of the refractive index changes, light modulation of the reflected beam 5 signal is performed by changing the mode coupling efficiency without changing the waveguide mode angle.

Therefore, when the refractive index of the optical waveguide 3 is changed by using the pump beam 7, the angle of the waveguide mode of the optical waveguide 3 is changed to change the reflectivity of the entire device. For example, in the graphs of FIGS. 4 and 5, if the refractive index is changed while the signal beam 4 is incident at an arbitrary incidence angle, the reflectivity at the incidence angle may vary continuously from 0 to 1, so that the light modulation and light switching This becomes possible.

On the other hand, Figure 6 is a graph showing the change in reflectivity according to the change in the refractive index of the optical waveguide 3 for each wavelength of the signal beam 4 when the incident angle is fixed. Each graph 600, 601, 602 in FIG. 6 shows a case where the absolute values of the refractive index change of the optical waveguide 3 are 0, 0.001 and 0.002, respectively. As shown, when the incident angle is fixed, the wavelength at which the waveguide mode is formed shifts according to the change in the refractive index of the optical waveguide 3. Therefore, it is also possible to use the optical element according to an embodiment of the present invention as a wavelength variable element or a wavelength selective filter element.

FIG. 7 is a graph showing an experimental result of measuring a change in reflectivity of an optical device while varying the intensity of the pump beam 7 in the optical device according to the first embodiment of the present invention. In particular, the reflectance curve change of the TE ₀ mode among the waveguide modes of the signal beam 4 is shown.

The optical device used in the experiment was composed of an SF10 prism (1), a 700 nm thick MgF ₂ coupling layer (2) and a 3 μm thick Au (1% by volume): SiO ₂ nanocomposite optical waveguide (3). . The pump beam 7 used a 532 nm wavelength high-power continuous wave (CW) laser corresponding to the surface plasmon resonance wavelength band of Au nanoparticles, and the CW laser of 1550 nm wavelength was used as the signal beam 4. Used.

Each graph 700, 701, 702, 703 in FIG. 7 shows a reflectance curve when the intensity of the pump beam 7 is 0, 20, 60 and 120 mW. As shown in the figure, as the intensity of the pump beam 7 increases, the shape of the reflectivity curve gradually shifts toward the low angle only the waveguide mode angle without large change. Based on the initial dip position of the graph 700 in the state where the pump beam 7 is turned off, the reflectivity changes according to the intensity change of the pump beam 7, and the intensity of the pump beam 7 is 120 mW. It can be seen at 703 that complete signal modulation is achieved.

8 shows the time response characteristic of the reflected optical signal 5 according to the on / off of the pump beam 7 in the optical device according to the first embodiment of the present invention. When the pump beam 7 is irradiated, the intensity of the emission signal beam 5 initially increases rapidly and then gradually saturates and remains at a specific value, and rapidly decreases when the pump beam 7 is turned off. On the other hand, the switching operation on the CW pump beam 7 is also attributable to the thermo-optic effect due to resonance absorption.

9 is a graph showing the results of irradiating the pump beam 7 of a single pulse having a pulse width of 5 ns with respect to the optical device according to the first embodiment of the present invention. As the pump beam 7, a high power Q-switched Nd: YAG laser having a wavelength of 532 nm was used. At this time, the energy of the pump beam 7 is 1.2 mJ, and the intensity of the pump beam 7 focused on the lens at the point where the signal beam 4 is coupled to the optical waveguide 3 is about 6.79 MW / cm ² . Has

When the single pump pulse beam 7 is irradiated for the TE ₀ mode in the waveguide mode, the intensity of the reflected signal beam 5 shows an initial rapid increase and the initial state through a slightly gentle thermal relaxation behavior after a sharp drop with the disappearance of the pulse. Return to When the pump beam 7 of intensity of about 6.79 MW / cm ² described above is used, the tertiary nonlinear optical characteristics expressed in the metal nanocomposite material coexist with electronic nonlinearity and thermal nonlinearity, in particular, the contribution of thermal nonlinearity. Is high. Therefore, the response characteristics can be improved when employing a material system or device structure that facilitates the thermal relaxation process.

In general, the method of smoothing the thermal relaxation process is to use a material with high thermal conductivity in at least one of the matrix materials of the nanocomposite included in the prism (1), the coupling layer (2), or the optical waveguide (3). desirable. In one embodiment of the present invention, the coupling layer 2 is formed of a metal material having excellent heat conduction characteristics.

The metal material constituting the coupling layer 2 may be a metal whose optical properties are controlled by the Drude free electron model and the real term of the complex refractive index is smaller than that of the prism (1) or the optical waveguide (3). have. Preferably, precious metals such as Ag, Au, and Cu, and alloys containing these elements as main components, which have a low absorption rate of the material itself and have a real term of complex refractive index less than 1, can enhance the mode restraining effect of the waveguide 4. It can be used for the coupling layer 2.

In addition, a transparent conductive oxide such as indium-tin-oxide (ITO) exhibiting metallic properties at or below the surface plasma frequency can also be used as the coupling layer 2. In an embodiment of the present invention, the thickness of the coupling layer 2 may be adjusted to be thinner than or equal to the skin depth to facilitate optical coupling of the signal beam 4 to the waveguide mode.

The graphs 100 and 101 of FIG. 10 show optical signal responses in the case of using a coupling layer 2 composed of MgF ₂ and a coupling layer composed of Au, respectively. As shown, the graph 101 in the case of using the coupling layer 2 composed of Au is higher than the graph 100 in the case of using the coupling layer 2 composed of MgF ₂ . It can be seen that all the time is reduced.

When Au is used as the coupling layer 2, the refractive index is smaller than when MgF ₂ is used. In addition, the mode restraining effect of the optical waveguide 3 is greatly enhanced, and thus, the thickness of the nanocomposite can be lowered, and consequently, there is an advantage that the heat accumulation effect of the nanocomposite material itself can be reduced by mass reduction. In addition, the surface plasmon polariton excited at the interface between the coupling layer (2) consisting of Au and the nanocomposite of the optical waveguide (3) when the TM mode under the P wave condition is used compared to the TE mode under the S wave condition. polariton) enhances the coupling efficiency.

FIG. 11 shows the TE ₀ mode of the signal beam 4 when a single pulse pump beam 7 having a pulse width of 30 ps is incident in order to confirm the optical switch operation by pure electronic tertiary nonlinearity rather than thermal nonlinearity. It is a graph showing the optical signal response. The pump beam 7 was formed to have an intensity of 0.47 GW / cm ² using an Nd: YAG laser of 532 nm wavelength, and the wavelength of the signal beam 4 was 1550 nm.

As shown, the light switching operation was performed by the cross modulation method between the pump beam 7 of 532 nm wavelength and the signal beam 4 of 1550 nm wavelength corresponding to the surface plasmon resonance wavelength. The graph of FIG. 11 shows that a high nonlinear optical coefficient and a fast response speed can be simultaneously obtained by an optical device according to an embodiment of the present invention.

12 is a longitudinal sectional view schematically showing an optical device according to a second embodiment of the present invention. Referring to FIG. 12, the optical device according to the embodiment includes an optical transmission unit 1, 2, 8, 9 and an optical waveguide 3, and the optical transmission unit includes a prism 1 and an index matching oil layer ( 9), the substrate 8 and the coupling layer 2 are configured.

Unlike the first embodiment in which the optical waveguide 3 is formed directly on the bottom of the prism 1, the second embodiment uses a substrate 8 made of an optically transparent material such as silica glass. The coupling layer 2 is optically connected to the bottom of the substrate 8, and the index matching oil layer 9 is positioned on the top surface of the substrate 8. Substrate 8 is coupled to prism 1 using an index matching oil layer 9.

The operation of the optical device according to the second embodiment of the present invention configured as described above is the same as the optical device according to the first embodiment described above. However, since the deposition process using the flat substrate 8 can be used without directly forming the optical waveguide 3 on the bottom of the prism 1, there is an advantage in that the process control for improving the film quality is easy.

In one embodiment of the invention, the refractive index of the substrate 8 is preferably equal to or greater than the refractive index of the prism 1. In addition, the refractive index of the index matching oil layer 9 is preferably equal to the refractive index of the prism 1 or the substrate 8 or has a value between the refractive index of the prism 1 and the refractive index of the substrate 8. As the material of the substrate 8, any material that is optically transparent to the wavelength of the signal beam 4 can be used without limitation of organic or inorganic materials.

13 is a longitudinal sectional view schematically showing an optical device according to a third embodiment of the present invention. Referring to FIG. 13, in the above embodiment, the light transmitting units 10 and 2 are formed of the prism 10 and the coupling layer 2 in the same manner as in the first embodiment.

However, in the third embodiment, the prism 10 is composed of a cylindrical prism 10 having a hemispherical cross section located on the plane formed by the signal beam 4 and the pump beam 7. When the cylindrical prism 10 is used as in the above embodiment, the light beam is incident on the process of passing through the interface with the prism 10 by the signal beam 4 incident on the prism 1 in a direction perpendicular to the hemispherical surface from the outside. The path is not refracted.

Therefore, the position where the signal beam 4 reaches the interface between the prism 10 and the coupling layer 2 changes during the process of changing the incident angle of the prism 10 of the signal beam 4 to form the waveguide mode. I never do that. Therefore, it is easy to align the pump beam 7 at the point where the signal beam 4 is coupled onto the optical waveguide 3, and even if the incident angle of the prism 10 of the signal beam 4 changes, There is an advantage that the alignment of the incident positions of the beam 4 and the pump beam 7 can be maintained.

14 is a longitudinal sectional view schematically showing an optical device according to a fourth embodiment of the present invention. Referring to FIG. 14, in the above-described embodiment, the light transmitting units 11 and 2 are formed of the prism 11 and the coupling layer 2 in the same manner as in the first embodiment.

However, in the fourth embodiment, the prism 11 has a trapezoidal longitudinal section. The first face, i.e., the bottom, of the trapezoidal prism 11 is optically connected to the coupling layer 2, and the second face, i.e., the top, of the prism 11 is formed parallel to the bottom and spaced apart from the bottom. The pump beam 7 enters the upper surface of the prism 11, passes through the trapezoidal prism 11, and reaches the coupling layer 2 connected to the bottom surface of the prism 11.

When configured as in the above embodiment, as the pump beam 7 reaches the bottom of the prism 11, the intensity becomes weak due to light absorption by the constituent materials of the optical waveguide 3 as in the first embodiment. Can be prevented. In addition, when there is no obstacle causing the light absorption of the pump beam 7, the observation of the incident point is easy, there is an advantage that the alignment of the incident position of the signal beam 4 and the pump beam 7 is easy.

15 is a longitudinal sectional view schematically showing an optical device according to a fifth embodiment of the present invention. The optical device according to the fifth embodiment is basically similar to the optical device according to the fourth embodiment, except that the light source unit 12 is optically connected to the upper surface of the prism 11 through the bonding layer 13. There is.

The light source unit 12 is used as a resonant wavelength band light source, and irradiates the pump beam 14 vertically emitted into the prism 11. When integrating the light source unit 12 with the prism 11 as in the above embodiment, there is an advantage that the overall device configuration can be simplified. In one embodiment of the present invention, the light source unit 12 may be composed of an array of a plurality of light sources, and when using the arrayed pump beam 14 output from the light source unit 12 and the signal beam (4) There is an advantage that the spatial tolerance between the pump beams 14 is increased.

The optical devices according to the first to fifth embodiments of the present invention described above have disclosed a configuration in which a signal beam is coupled to an optical waveguide using a prism and a coupling layer. However, this is merely illustrative, and in another embodiment of the present invention, it is also possible to convert the signal beam into a specific waveguide mode beam by coupling the signal beam to the surface of the optical waveguide using a surface grating instead of the prism and the coupling layer as the light transmission unit. .

In addition, since the prism is used in the first to fifth embodiments described above, the device is operated using a signal beam totally reflected at the interface between the prism on the bottom of the prism and the coupling layer. However, in one embodiment of the present invention, the surface grating may be optically connected to the other side of the optical waveguide in which the light transmission unit is connected to one side to allow the signal beam to pass through the optical waveguide.

For example, when applied to the first embodiment of the present invention shown in FIG. 1, the surface grating may be connected to the bottom of the optical waveguide 3 not connected to the prism 1. In this case, the signal beam incident on the optical waveguide from the light transmitting unit passes through the optical waveguide and exits through the surface grating, and the intensity of the signal beam passing through the optical waveguide is controlled by the pump beam.

An optical device according to embodiments of the present invention described above is a device using a waveguide mode coupling characteristic that directly responds to a change in refractive index of a nonlinear optical material, unlike an interferometric switch device using a relative phase difference between signal beams. Therefore, the signal beam does not need to propagate in the waveguide for phase change, and it is possible to operate if the transverse wave component in the thickness direction of the waveguide can form only the waveguide mode.

Therefore, using the optical device according to the embodiments of the present invention and the operation method described above, since the optical switch operation method that depends on the refractive index change of the nonlinear optical material itself is applied, the excellent nonlinear optical characteristics of the resonant nanocomposite While using it to the maximum, there is an advantage that can improve the device response characteristics by reducing the accompanying absorption loss. In addition, the configuration of the device is simplified, there is an advantage that can be operated by improving the sensitivity of the device.

Although the present invention described above has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and variations may be made therefrom. However, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (18)

A light transmission unit through which the signal beam propagates; And And an optical waveguide optically connected to the light transmitting unit, the signal beam propagated from the light transmitting unit propagating at a waveguide mode angle, and a pump beam incident at the same point as the point at which the signal beam is incident. The wavelength of the signal beam and the wavelength of the pump beam is different from each other, And the waveguide mode angle of the optical waveguide is determined by the pump beam. The method of claim 1, The light transmission unit, A prism in which the signal beam is incident and propagated; And And a coupling layer optically coupled to the prism for coupling the signal beam propagated at a waveguide mode angle to the optical waveguide. The method of claim 2, An optically transparent substrate positioned between the prism and the coupling layer; And And an index matching oil layer disposed between the substrate and the prism and bonding the substrate and the prism. The method of claim 2, The cross section of the prism in the plane direction including the signal beam and the pump beam is a hemispherical shape. A light transmission unit through which the signal beam and the pump beam are propagated; And And an optical waveguide optically connected to the light transmitting unit, wherein the pump beam and the signal beam propagated at the waveguide mode angle from the light transmitting unit are incident at the same position. The wavelength of the signal beam and the wavelength of the pump beam is different from each other, And the waveguide mode angle of the optical waveguide is determined by the pump beam. The method of claim 5, The light transmission unit, A prism including a first surface on which the pump beam is incident and a second surface parallel to the first surface and spaced apart from the first surface; And And a coupling layer optically coupled to the second surface of the prism, the coupling layer coupling the signal beam propagated from the pump beam and the prism at a waveguide mode angle to the optical waveguide. The method of claim 6, The light transmission unit, A bonding layer optically coupled to the first face of the prism; And And a light source unit optically connected to the bonding layer to incident the pump beam to the prism. The method of claim 7, wherein The light source unit includes a plurality of light sources arranged in an array (array) form. The method according to claim 1 or 5, And the light transmitting part includes a surface grating optically connected to the optical waveguide. The method according to claim 1 or 5, The light transmitting unit is connected to one side of the optical waveguide, And a surface grating optically connected to the other side of the optical waveguide for emitting the signal beam incident on the optical waveguide. The method according to claim 1 or 5, The optical waveguide includes an optical nanocomposite in which metal nanoparticles or semiconductor nanoparticles are dispersed in an optically transparent matrix material. The method of claim 11, The metal nanoparticles are Au, Ag, Cu, Al, In, Sn, Pb, Sb, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Ru, Rh, Pd, Ta, At least one selected from the group consisting of W, Pt, and the alloy of the material. The method of claim 11, The semiconductor nanoparticles, Si, Ge, CdS, CdSe, CdTe, CuBr, AgBr, CuCl, InP, GaP, GaAs, InAs and characterized in that any one or more selected from the group consisting of solid solutions and compounds between the above Optical element. The method of claim 11, The transparent matrix-based material is SiO ₂ , TiO ₂ , ZrO ₂ , HfO ₂ , Al ₂ O ₃ , CdO, ZnO, In ₂ O ₃ , SnO ₂ , Ga ₂ O ₃ , Y ₂ O ₃ , BeO, MgO, WO Oxides comprising ₃ , V ₂ O ₃ , BaTiO ₃ and PbTiO ₃ ; Si ₃ N ₄ And nitrides comprising Al ₃ N ₄ ; Phosphides including InP and GaP; Sulfides including ZnS and As ₂ S ₃ ; _{MgF 2, CaF 2, NaF,} BaF 2, PbF 2, a fluoride containing LiF, and LaF; Selenides including ZnSe; An inorganic material comprising a mixture of one or more of the above oxides, nitrides, phosphides, sulfides, fluorides and selenides; Organic materials including polycarbonate and polymethyl methacrylate (PMMA); Mixtures of the organic materials; And at least one selected from the group consisting of a composite of the organic material. The method according to claim 2 or 6, And the refractive index of the coupling layer is smaller than the refractive index of the prism and the refractive index of the optical waveguide. The method according to claim 2 or 6, And the coupling layer comprises MgF ₂ . The method according to claim 2 or 6, The coupling layer is an optical device, characterized in that it comprises a metal containing Au, Ag and Cu and an alloy containing the metal. In the method of operating the optical device according to claim 1, Injecting the signal beam to the light transmitting part for incident on the optical waveguide at a waveguide mode angle; And And injecting the pump beam to determine the waveguide mode angle of the optical waveguide at the same point as the point where the signal beam is incident on the optical waveguide.