A tunable dual-channel photon filter

Abstract

The present invention provides an adjustable dual-channel photon filter, belonging to the field of optical technology. It includes five first dielectric layers and three second dielectric layers, and the first dielectric layer and the second dielectric layer are arranged in the order of the incident direction to the exit direction: the first dielectric layer, the second dielectric layer, the first dielectric layer, the first dielectric layer, the first dielectric layer, the second dielectric layer, the first dielectric layer, the second dielectric layer; the first dielectric layer and the second dielectric layer are two uniform dielectrics with different refractive indices; the thickness of the first dielectric layer and the second dielectric layer is 1 / 4 of the optical wavelength corresponding to their respective refractive indices; a graphene monolayer is embedded at the boundary of adjacent first dielectric layers or at the boundary of the first dielectric layer and the second dielectric layer; the transverse magnetic wave is vertically incident from the incident side of the adjustable dual-channel photon filter. The dual-channel photon filter can adjust the transmittance and center frequency of the filter channel.

Description

Technical Field

[0001] The invention belongs to the technical field of optics and relates to an adjustable dual-channel photon filter. Background Art

[0002] There are four types of filters: bandpass, bandstop, low-pass and high-pass. In multi-channel communications, multi-channel filters are needed to filter single frequencies. In optical fiber communication systems, wavelength division multiplexing technology can be used to increase channel capacity, and the optical wavelength division multiplexer used is a multi-channel device. Traditional optical wavelength division multiplexers use fiber gratings to achieve channel demultiplexing. The emergence of artificial photonic crystals provides a new solution for the design of multi-channel filters in wavelength division multiplexing technology.

[0003] By arranging two dielectrics with different refractive indices alternately in space, one can obtain one-dimensional, two-dimensional or three-dimensional photonic crystals. Photonic crystals have a band structure, which can achieve total transmission and total reflection of light waves. Defective modes will appear in the energy band of defective photonic crystals. When the wavelength of the incident light is equal to the defective mode, a resonant output will be formed, at which time the transmittance is extremely large and the reflection is extremely small. This type of structure can be used in single-channel photonic filters.

[0004] Non-periodic photonic crystals also have band structures, but the order of non-periodic photonic crystals is not as good as that of periodic photonic crystals. However, non-periodic photonic crystals naturally have multiple defect layers, which makes it easier for non-periodic photonic crystals to obtain multiple resonant defect modes. The order of quasi-periodic photonic crystals is between periodic photonic crystals and non-periodic photonic crystals. In quasi-photonic crystals, multiple resonant defect modes can be obtained, and the number of defect modes can be expanded by increasing the sequence number. Therefore, quasi-periodic photonic crystals can be used as multi-channel photonic filters. However, once the photonic crystal is formed, the position of the defect layer is fixed, and it is difficult to control the center frequency of the defect mode.

[0005] Graphene is an ultra-thin two-dimensional material whose surface conductivity can be flexibly controlled by the chemical potential of graphene. When graphene is equivalent to a dielectric of a certain thickness, its equivalent refractive index is a function of the chemical potential. Therefore, the equivalent refractive index of graphene can be flexibly controlled by the chemical potential. If graphene is embedded in a photonic crystal, the presence of graphene will cause a change in the transmittance of the overall structure. The equivalent refractive index of graphene is a function of the chemical potential, and the transmission spectrum of the structure can be changed by the chemical potential of graphene, thereby achieving the purpose of controlling the center frequency of the transmission mode.

[0006] Mathematically, the period-doubling (PD) sequence is a quasi-periodic sequence, and its corresponding PD photonic crystal is a quasi-periodic photonic crystal. In PD photonic crystals, there are a series of transmission modes. These transmission modes are formed by the resonance of light waves in the defect layer. As the sequence number increases, the number of defect modes expands rapidly, and the defect modes have self-similar characteristics. This phenomenon is called the optical fractal effect, and the corresponding resonant mode is also called the optical fractal morphology. Optical fractal morphology can be applied to multi-channel optical filters. Graphene is then inserted into the PD photonic crystal to form a composite structure, and the center frequency and transmittance of the filter channel can be flexibly controlled by the chemical potential of graphene. Summary of the invention

[0007] The purpose of the present invention is to provide an adjustable dual-channel photon filter in view of the above-mentioned problems existing in the prior art. The technical problem to be solved by the present invention is to design a dual-channel photon filter capable of adjusting the transmittance and center frequency of the filtering channel.

[0008] The object of the present invention can be achieved through the following technical solutions: an adjustable dual-channel photon filter, characterized in that two dielectric sheets are arranged in sequence according to a period-doubling (PD) sequence with a sequence number N=3 to form a PD photon crystal, and graphene is embedded in the interface between two adjacent sheets to form a composite structure. Specifically, it includes five first dielectric layers and three second dielectric layers, and the first dielectric layer and the second dielectric layer are arranged in the order of: first dielectric layer, second dielectric layer, first dielectric layer, first dielectric layer, first dielectric layer, second dielectric layer, first dielectric layer, second dielectric layer from the incident direction to the exit direction; the first dielectric layer and the second dielectric layer are two uniform dielectrics with different refractive indices; the thickness of the first dielectric layer and the second dielectric layer is 1 / 4 of the optical wavelength corresponding to their respective refractive indices; a graphene monolayer is embedded in the boundary between adjacent first dielectric layers or the boundary between the first dielectric layer and the second dielectric layer; the transverse magnetic wave is vertically incident from the incident side of the adjustable dual-channel photon filter.

[0009] Furthermore, the first dielectric layer is lead telluride, and the second dielectric layer is cryolite.

[0010] Furthermore, the adjustable dual-channel photon filter has a dual-wavelength resonant optical fractal form, corresponding to two transmission modes. The two transmission modes can be used for dual-channel photon filtering, and the transmittance and center frequency of the two filter channels are regulated by the chemical potential of the graphene monolayer. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the composite structure of a dual-channel photon filter.

[0012] Figure 2 It is the transmission spectrum of the composite structure of PD photonic crystal and graphene.

[0013] Figure 3 is the transmission spectrum corresponding to different graphene chemical potentials.

[0014] Figure 4 (a) is the relationship between the transmittance of channel 1 and the chemical potential of graphene; Figure 4 (b) The relationship between the normalized frequency of channel 1 and the chemical potential of graphene; Figure 4 (c) Transmittance of channel 2 versus graphene chemical potential; Figure 4 (d) The normalized frequency of channel 2 as a function of the chemical potential of graphene.

[0015] In the figure, H, the first dielectric layer; L, the second dielectric layer; G, the graphene monolayer. DETAILED DESCRIPTION

[0016] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0017] like Figure 1 The composite structure of period-doubling (PD) photonic crystal and graphene with serial number N=3 is given, where H is the high refractive index material lead telluride, and its refractive index is n H =4.1; L is the low refractive index material cryolite, whose refractive index is n L =1.35. The incident light is a transverse magnetic wave, incident vertically from the left. Symbol I i is the incident light, I o is the transmitted light. The thickness of H and L is 1 / 4 of the optical wavelength, that is, the thickness of H is d H =λ0 / 4 / n H = 0.0945 μm (μm means micrometer), where λ0 = 1.55 μm is the central wavelength, and the thickness of L is d L =λ0 / 4 / n L =0.287μm. The dielectrics H and L are arranged in sequence according to the PD sequence rule of N=3, and then graphene is embedded in the interface between two adjacent dielectric sheets. G represents graphene, which is an ultra-thin two-dimensional material. Compared with the thickness of the dielectric sheets H and L, the thickness of graphene can be ignored. The composite structure can be expressed as HGLGHGHGHGLGHGL.

[0018] Mathematically, the iteration rule of the PD sequence is: S0 = H, S1 = HL, S2 = HLHH, ..., S N =S N-1 SN- 2S N-2 , ..., where N (N = 0, 1, 2, 3, ...) is the sequence number, S N Indicates the Nth item of the sequence. In the corresponding PD photonic crystal, the letters H and L represent two uniform dielectric sheets with high and low refractive indices, respectively.

[0019] When the photonic crystal does not contain graphene, the transverse magnetic wave is incident vertically. Figure 2 The transmission spectrum of the PD photonic crystal corresponding to serial number N = 3 is given. The ordinate T represents the transmittance, and the abscissa is (ω-ω0) / ω gap represents the normalized angular frequency, where ω = 2πc / λ, ω0 = 2πc / λ0 and ω gap =4ω0arcsin│(n a -n b ) / (n a +n b )| 2 / π represent the incident light angular frequency, the incident light center angular frequency and the angular frequency band gap, respectively. c is the speed of light in a vacuum, and arcsin is the inverse sine function. It can be seen that there is a photon band gap in the normalized frequency interval (-1,1). In the middle of the band gap, two resonance peaks appear, corresponding to two filter channels, marked with *. From left to right, these two channels are named channel 1 and channel 2 in order.

[0020] When graphene is inserted into the PD photonic crystal with N=3, the graphene is located at the interface between two adjacent dielectric sheets, forming a composite structure of PD photonic crystal and graphene. Figure 3 The transmission spectra corresponding to different graphene chemical potentials in the composite structure are given. It can be seen that when the chemical potential of graphene changes, the transmission spectra of the light waves do not overlap. However, there are two transmission peaks in the band gap of each spectrum line, corresponding to channel 1 and channel 2, marked with ovals. However, as the chemical potential of graphene changes, the center frequency of the transmission peak moves slightly, and the peak value of the transmission peak is also affected. Therefore, when the composite structure is used as a dual-channel photon filter, the transmittance and center frequency of the filter channel can be flexibly controlled by the chemical potential of graphene.

[0021] Will Figure 3 The transmittance corresponding to channel 1 is denoted as T1, and the corresponding transmission mode center frequency is denoted as ω1; the transmittance corresponding to channel 2 is denoted as T2, and the corresponding transmission mode center frequency is denoted as ω2. Figure 4 (a) shows the relationship between the transmittance T1 of channel 1 and the chemical potential of graphene. It can be seen that when μ c When ≤0.25eV, T1=0.7196; when μ c>0.25eV, T1≈0.967. Transmittance T1 at chemical potential μ c There is an upward jump at =0.3eV. Figure 4 (b) shows the relationship between the transmission mode center frequency ω1 of channel 1 and the chemical potential of graphene. It can be seen that when μ c When μ ≤0.3eV, the transmission mode center frequency decreases as the chemical potential of graphene increases; c When the chemical potential of graphene increases, the transmission mode center frequency increases. c =0.3eV is the minimum.

[0022] Figure 4 (c) shows the relationship between the transmittance T2 of channel 2 and the chemical potential of graphene. It can be seen that when μ c When ≤0.45eV, T2=0.7166; when μ c When the chemical potential of graphene increases, the transmittance increases. c After >0.55eV, it gradually tends to saturation, and the saturation value is about T2=0.967. Figure 4 (b) shows the relationship between the transmission mode center frequency ω2 of channel 2 and the chemical potential of graphene. It can be seen that when μ c When μ ≤0.5eV, the transmission mode center frequency decreases as the chemical potential of graphene increases; c When the chemical potential of graphene increases, the transmission mode center frequency increases. c =0.5eV is the minimum.

[0023] In summary, there are two adjustable optical fractal forms in the composite structure of PD photonic crystal and graphene with serial number N=3, corresponding to two transmission modes. These two transmission modes can be used in dual-channel photonic filters, and the transmittance and center frequency of the filter channel can be flexibly controlled by the chemical potential of graphene at the same time.

[0024] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. An adjustable dual-channel photon filter, characterized in that: The invention comprises five first dielectric layers and three second dielectric layers, wherein the first dielectric layers and the second dielectric layers are arranged in the following order from the incident direction to the exiting direction: the first dielectric layer, the second dielectric layer, the first dielectric layer, the first dielectric layer, the first dielectric layer, the second dielectric layer, the first dielectric layer, the second dielectric layer; the first dielectric layer and the second dielectric layer are two uniform dielectrics with different refractive indices; The thickness of the first dielectric layer and the second dielectric layer is 1 / 4 of the optical wavelength corresponding to their respective refractive indices; a graphene single layer is embedded in the boundary between adjacent first dielectric layers or the boundary between the first dielectric layer and the second dielectric layer; and the transverse magnetic wave is vertically incident from the incident side of the adjustable dual-channel photon filter.

2. The adjustable dual-channel photon filter according to claim 1, characterized in that: The first dielectric layer is lead telluride, and the second dielectric layer is cryolite.

3. The adjustable dual-channel photon filter according to claim 1 or 2, characterized in that: The adjustable dual-channel photon filter has an optical fractal form of dual-wavelength resonance, corresponding to two transmission modes; the two transmission modes can be used for dual-channel photon filtering, and the transmittance and center frequency of the two filtering channels are regulated by the chemical potential of the graphene monolayer.

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