A dispersionless coupled mode spot size converter

Abstract

The present application relates to a kind of dispersion-free coupling mode spot converters, comprising: wide input straight waveguide, multiple periodic S-shaped cosine curved waveguide, multiple narrow output straight waveguide, the two ends of the S-shaped cosine curved waveguide structure are used to couple wide input straight waveguide and narrow output straight waveguide, by the coupling coefficient between the S-shaped cosine curved waveguide between proper adjustment, realize the dispersion-free coupling between optical waveguide in turn make wide input optical wave signal can be more gathered from center narrow waveguide output.Compared with traditional single linear taper mode spot converter, the mode spot converter provided by the present application can realize high-efficiency coupling in shorter gradual length range, greatly improve the integration of photonic chip.

Description

Technical Field

[0001] This invention relates to the field of integrated photonic chips, and more specifically to a dispersion-free mode-spot converter. Background Technology

[0002] Fiber optic (3D waveguide)-planar waveguide couplers are widely used in integrated optics. A key challenge in coupling optical waveguide chips to fiber optics is the significant difference in cross-sectional dimensions between the fiber and the waveguide (lithium niobate waveguide, silicon waveguide, silicon nitride waveguide). Typically, standard single-mode fiber and waveguide have cross-sectional dimensions in the micrometer and sub-micrometer ranges, respectively. Direct coupling results in severe mode mismatch and reduces coupling efficiency, hindering the full performance of the device and limiting its practical application. To overcome this bottleneck, couplers are introduced into the chip to connect the fiber and the waveguide chip. Tapered mode converters, as one type of coupler, expand or shrink the mode field size by changing the waveguide dimensions to match the mode field of the planar waveguide.

[0003] Traditional tapered mode converters consist of a single tapered waveguide with a linearly varying width, connecting a three-dimensional optical waveguide to a planar waveguide to achieve mode field conversion. To achieve high coupling efficiency (above 95%), the mode converter needs to be very long, for example, 200 μm or even more than 500 μm. This is detrimental to the integration of photonic chips and is also highly sensitive to waveguide structure (waveguide coupling spacing, waveguide width, wavelength). Therefore, there is an urgent need for a solution that can shorten the length of the tapered waveguide while remaining insensitive to waveguide structure. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a dispersion-free coupled mode spot converter.

[0005] To achieve the above objectives, the technical solution of the present invention is a dispersion-free coupled mode-spot converter, specifically comprising:

[0006] Wide input straight waveguide, multiple periodic S-shaped cosine bend waveguides, and multiple narrow output straight waveguides.

[0007] The two ends of the S-shaped cosine waveguide structure are used to couple a wide-input straight waveguide and a narrow-output straight waveguide. By properly adjusting the coupling coefficient between the S-shaped cosine waveguides, dispersion-free coupling between the optical waveguides can be achieved, thereby enabling the wide-input optical signal to be more focused and output from the central narrow waveguide.

[0008] Furthermore, the periodic S-shaped cosine curved waveguide is composed of multiple cosine boundary gradient profile waveguides.

[0009] Furthermore, the periodic S-shaped cosine-bent waveguide is insensitive to wavelength, waveguide width, and waveguide coupling spacing.

[0010] Furthermore, the coupling coefficient is adjusted by the amplitude, period, effective refractive index of the optical waveguide, incident light wavelength, and waveguide spacing of the S-shaped cosine curved waveguide.

[0011] Furthermore, the expression for the coupling coefficient is:

[0012] Where c is the coupling coefficient between the periodic S-shaped cosine waveguides; A is the amplitude of the S-shaped cosine waveguide; n eff denoted as the effective refractive index of the waveguide material; P is the period of the S-shaped cosine bend waveguide; w1 and w2 are the input and output waveguide widths of the cosine boundary gradient profile, respectively; g is the spacing between the periodic S-shaped cosine bend waveguides; z is the direction of optical wave propagation; λ is the incident light wavelength; and J0 is the zero-order Bessel function.

[0013] Furthermore, let If the coupling coefficient is less than 0 or greater than 0, positive and negative coupling between periodic S-shaped cosine curved waveguides can be achieved, thereby enabling wide input optical signals to be output more concentratedly from the central narrow waveguide.

[0014] Furthermore, the materials used in the optical waveguide include, but are not limited to, lithium niobate thin film materials, silicon nitride thin film materials, and silicon materials.

[0015] Furthermore, the fabrication processes used for the optical waveguide include, but are not limited to, ICP etching, dry etching, wet etching, and femtosecond laser-assisted chemical mechanical polishing.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) In terms of the gradient length of the mode converter, the gradient waveguide length is greatly shortened, which greatly improves the integration of the integrated photonic chip.

[0018] (2) Regarding the sensitivity to waveguide structure, it is not sensitive to waveguide structure (waveguide coupling spacing, waveguide width, wavelength), which greatly reduces the processing difficulty of waveguide structure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the dispersion-free coupled mode-spot converter structure of the present invention;

[0020] Figure 2 This is a diagram showing the optical field transmission distribution of the dispersion-free coupled mode converter under different waveguide coupling spacings according to the present invention.

[0021] Figure 3 This is the optical field transmission distribution diagram of a traditional single-width linearly varying tapered mode converter;

[0022] Figure 4 This is an optical field transmission distribution diagram of the dispersion-free coupled mode converter under different waveguide widths according to the present invention;

[0023] Figure 5 This is a diagram showing the optical field transmission distribution of the dispersion-free coupled mode converter under different incident light wavelengths according to the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the scope of protection of the present invention.

[0025] Please see Figure 1 , Figure 1 This is a schematic diagram of the dispersion-free coupled mode-spot converter structure of the present invention. As shown in the figure, a dispersion-free coupled mode-spot converter includes: a wide input straight waveguide 1, multiple periodic S-shaped cosine curved waveguides 2, and multiple narrow output straight waveguides 4.

[0026] The two ends of the S-shaped cosine curved waveguide 2 structure are used to couple the wide input straight waveguide 1 and the narrow output straight waveguide 4. By properly adjusting the coupling coefficient between the S-shaped cosine curved waveguide 2, dispersion-free coupling between the optical waveguides can be achieved, thereby enabling the wide input optical wave signal to be more focused and output from the central narrow waveguide 5.

[0027] The periodic S-shaped cosine curved waveguide 2 is composed of multiple cosine boundary gradient profile waveguides 3.

[0028] The periodic S-shaped cosine-bent waveguide 2 is insensitive to wavelength, waveguide width, and waveguide coupling spacing.

[0029] Specifically, the coupling coefficient is adjusted by the amplitude, period, effective refractive index of the optical waveguide, incident light wavelength, and waveguide spacing of the S-shaped cosine curved waveguide 2.

[0030] The expression for the coupling coefficient is:

[0031] Where c is the coupling coefficient between the periodic S-shaped cosine waveguides; A is the amplitude of the S-shaped cosine waveguide; n eff denoted as the effective refractive index of the waveguide material; P is the period of the S-shaped cosine bend waveguide; w1 and w2 are the input and output waveguide widths of the cosine boundary gradient profile, respectively; g is the spacing between the periodic S-shaped cosine bend waveguides; z is the direction of optical wave propagation; λ is the incident light wavelength; and J0 is the zero-order Bessel function.

[0032] Specifically, let If the coupling coefficient is less than 0 or greater than 0, positive and negative coupling between periodic S-shaped cosine curved waveguides can be achieved, thereby enabling the wide input optical signal 1 to be output more concentratedly from the central narrow waveguide 5.

[0033] Specifically, the materials used in the optical waveguide include, but are not limited to, lithium niobate thin film materials, silicon nitride thin film materials, and silicon materials.

[0034] Specifically, the fabrication process used for the optical waveguide includes, but is not limited to, ICP etching, dry etching, wet etching, and femtosecond laser-assisted chemical mechanical polishing.

[0035] Figure 2 Simulation results of optical field transmission for a dispersive mode-spot converter under different coupling spacings are presented. With an input waveguide 1 diameter of 5.8 μm, an output waveguide 5 diameter of 0.5 μm, an optical wavelength of 1550 nm, a bent waveguide amplitude of 0.5 μm, a gradient input waveguide width of 1 μm, and a bent waveguide period of 10 μm, the optical field transmission is simulated from... Figure 2 As can be seen, the waveguide output coupling efficiency remains unchanged as the waveguide coupling spacing increases, indicating that the device is not sensitive to the waveguide coupling spacing (0.2 1 μm), which greatly improves the stability of the device. Figure 3 The simulation results show the optical field transmission of a traditional mode converter. Compared with the traditional mode converter, the gradient length of the dispersionless mode converter is greatly shortened by nearly 6 times while maintaining a matching coupling efficiency (95%) (the gradient length of this device is 35μm, while the traditional gradient length is 200μm), which greatly improves the integration of the device.

[0036] Figure 4 Simulation results of optical field transmission for a dispersive mode-effect converter under different gradient input waveguide widths are presented. With an input waveguide 1 diameter of 5.8 μm, an output waveguide 5 diameter of 0.5 μm, an optical wavelength of 1550 nm, a bent waveguide amplitude of 0.5 μm, a bent waveguide period of 10 μm, and a waveguide coupling spacing of 0.2 μm, the results are obtained from... Figure 4 It can be seen that as the width of the tapered input waveguide increases, the waveguide output coupling efficiency remains unchanged, indicating that the device is not sensitive to the width of the tapered input waveguide (0.8 1.6 μm), which greatly improves the stability of the device. Figure 5 Simulation results of optical field transmission for a dispersive mode-spot converter at different wavelengths are presented. Under the conditions of an input waveguide 1 diameter of 5.8 μm, an output waveguide 5 diameter of 0.5 μm, a bent waveguide amplitude of 0.5 μm, a bent waveguide period of 10 μm, a tapered input waveguide width of 1 μm, and a waveguide coupling spacing of 0.2 μm, the optical field transmission from... Figure 5 It can be seen that the waveguide output coupling efficiency does not change with the increase of wavelength, indicating that the device is not sensitive to optical wavelength (1.4 1.6 μm), which greatly improves the stability of the device.

[0037] The above-described embodiments are implementation methods of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the concept of the present invention, and these improvements and modifications all fall within the protection scope of the present invention.

Claims

1. A dispersion-free mode-spot converter, characterized in that, include: The system comprises a wide-input straight waveguide, multiple periodic S-shaped cosine bend waveguides, and multiple narrow-output straight waveguides, wherein the output end of the wide-input straight waveguide is coupled to the periodic S-shaped cosine bend waveguide and the narrow-output straight waveguide. The coupling coefficient c between the periodic S-shaped cosine-bent waveguides satisfies the following condition: Dispersion-free coupling between the optical waveguides is achieved, thereby enabling the optical signal to be output from the central narrow waveguide of the narrow output straight waveguide. In the formula, A is the amplitude of the periodic S-shaped cosine bending waveguide, and n eff denoted as , where is the effective refractive index of the periodic S-shaped cosine-bent waveguide material; P is the period of the periodic S-shaped cosine-bent waveguide; w1 and w2 are the input and output waveguide widths of the cosine-boundary gradient profile, respectively; g is the spacing between the periodic S-shaped cosine-bent waveguides; z is the direction of optical wave propagation; and λ is the incident light wavelength. It is a zero-order Bessel function; The periodic S-shaped cosine curved waveguide is composed of multiple cosine boundary gradient profile waveguides. The periodic S-shaped cosine-bent waveguide is insensitive to wavelength, waveguide width, and waveguide coupling spacing.

2. The dispersion-free coupled mode converter according to claim 1, characterized in that, The coupling coefficient is adjusted by the amplitude, period, effective refractive index, incident light wavelength, and spacing of the periodic S-shaped cosine waveguide.

3. The dispersion-free coupled mode converter according to claim 1, characterized in that, make If the coupling coefficient is less than 0 or greater than 0, positive and negative coupling between periodic S-shaped cosine curved waveguides can be achieved, thereby enabling wide input optical signals to be output more concentratedly from the central narrow waveguide.

4. The dispersion-free coupled mode converter according to claim 1, characterized in that, The optical waveguide is made of lithium niobate thin film material, silicon nitride thin film material, and silicon material.

5. The dispersion-free coupled mode converter according to claim 1, characterized in that, The fabrication process used for the optical waveguide includes, but is not limited to, ICP etching, dry etching, wet etching, and femtosecond laser-assisted chemical mechanical polishing.

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