An off-chip light emitting device

Abstract

The present invention relates to an off-chip light-emitting device, comprising: a substrate; a lower cladding layer located on the upper surface of the substrate and having a metal mirror embedded therein; a waveguide layer located on the upper surface of the lower cladding and comprising a waveguide and M-level concentric semicircular gratings; and an upper cladding layer located on the upper surface of the waveguide layer. The waveguide is configured to guide light into the M-level concentric semicircular gratings; the metal mirror is configured to reflect light leaking into the substrate toward the M-level concentric semicircular gratings; the M-level concentric semicircular gratings are configured to emit received light in a vertical direction. The slits of the first N levels of the M-level concentric semicircular gratings are etched to a lesser depth than the slits of the last K levels, where M = N + K and N ≤ M / 2. The present invention can improve the emission efficiency of the device.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an off-chip light emitting device. Background Art

[0002] Over the past few decades, silicon photonics technology based on the silicon-on-insulator (SOI) platform has made significant progress due to its compact footprint, high integration, low power consumption, and compatibility with complementary metal-oxide-semiconductor (CMOS) processes. Device design for optical transmission using Si materials is also crucial, and interlayer interconnection is the most important connection method in 3D optical interconnection technology.

[0003] The existing technology includes a single / double-layer interlayer grating coupler, which is a metal reflector on a Si / SiO2 / SiN multilayer material platform. It is used to couple light from a Si waveguide (lower layer) to a ring resonator coupled to an access waveguide on the SiN layer (top layer). It has a high peak coupling efficiency of up to 89% for a double-mirror structure and 64% for a single-mirror structure at telecom wavelengths. This opens up the possibility of low-loss 3D dense integration of optical functions in the hybrid material platform.

[0004] The prior art also proposed on-chip intra-layer and inter-layer grating couplers fabricated on a double-layer, single-crystal silicon nanomembrane. Simultaneous intra-layer coupling with a separated silicon photonic layer was demonstrated through the grating couplers. At a wavelength of 1550nm, the peak efficiency of each grating coupler was 18% and 44% at the bottom and top layers, respectively. The inter-layer grating coupler achieved an efficiency of 25% at a wavelength of 1560nm and a 3dB bandwidth of 41nm. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an off-chip light emitting device, which can improve the emission efficiency of the device.

[0006] The technical solution adopted by the present invention to solve the technical problem is to provide an off-chip light emitting device, comprising:

[0007] substrate;

[0008] a lower cladding layer, located on the upper surface of the substrate and having a metal mirror embedded therein;

[0009] a waveguide layer, located on the upper surface of the lower cladding, comprising a waveguide and an M-level concentric semicircular grating;

[0010] an upper cladding layer, located on an upper surface of the waveguide layer;

[0011] The waveguide is used to guide light into the M-level concentric semicircular grating; the metal mirror is used to reflect light leaked to the substrate to the M-level concentric semicircular grating; the M-level concentric semicircular grating is used to emit the received light in a vertical direction; the etching depth of the slits of the first N levels of the M-level concentric semicircular grating is less than the etching depth of the slits of the last K levels, wherein M=N+K, and N≤M / 2.

[0012] The waveguide layer further includes a narrow waveguide structure, which is located between the waveguide and the M-level concentric semicircular grating and is perpendicular to the waveguide.

[0013] The width of the narrow waveguide structure is smaller than the width of the waveguide.

[0014] The radius of the first-order circle of the M-order concentric semicircular grating is half the width of the waveguide.

[0015] The thickness of the metal mirror is 1 / 10 of the distance between the metal mirror and the waveguide layer.

[0016] The width of the slits of each level of the M-level concentric semicircular grating is the same, and the spacing between the slits of each level is the same.

[0017] Beneficial effects

[0018] Due to the adoption of the above-mentioned technical solution, the present invention has the following advantages and positive effects compared with the prior art: the present invention adopts a multi-level concentric semicircular grating, and designs the first several levels of the grating as shallow etched grooves. This design can facilitate the vertical emission of light, and a narrow waveguide structure is set between the multi-level concentric semicircular grating and the single-mode waveguide. The narrow waveguide structure reduces end face reflection, thereby reducing loss. In order to further reduce the loss caused by the sudden change of the end face, the radius of the first-level circle of the semicircular grating is designed to be half the width of the single-mode waveguide. The off-chip light emitting device of the present invention can achieve a vertical emission efficiency of more than 0.64 in the wavelength range of 1.16μm to 1.61μm, and the bandwidth covers multiple bands, making the device better for future wide-bandwidth applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0020] Figure 2 is a top view of a waveguide layer according to an embodiment of the present invention;

[0021] Figure 3 is a side view of an embodiment of the present invention;

[0022] Figure 4 1 is a mode field distribution diagram of the device at 1.55 μm when the TE0 mode is input in the embodiment of the present invention;

[0023] Figure 5 is a far-field diagram of the emission according to an embodiment of the present invention;

[0024] Figure 6 is the antenna pattern of an embodiment of the present invention;

[0025] Figure 7 is a graph showing how emission efficiency varies with wavelength according to an embodiment of the present invention;

[0026] Figure 8 This is a curve comparison of the emission efficiency of a device without a shallow etched grating and an embodiment of the present invention as a function of wavelength. DETAILED DESCRIPTION

[0027] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0028] The embodiments of the present invention relate to an off-chip light emitting device, such as Figure 1 As shown, it includes: a substrate 1; a lower cladding 2, located on the upper surface of the substrate 1 and having a metal mirror 5 embedded therein; a waveguide layer 3, located on the upper surface of the lower cladding 2, including a waveguide 6 and an M-level concentric semicircular grating 7; an upper cladding 4, located on the upper surface of the waveguide layer 3; the waveguide 6 is used to guide light into the M-level concentric semicircular grating 7; the metal mirror 5 is used to reflect light leaking into the substrate 1 to the M-level concentric semicircular grating 7; the M-level concentric semicircular grating 7 is used to emit the received light in a vertical direction; the etching depth of the slits of the first N levels of the M-level concentric semicircular grating 7 is less than the etching depth of the slits of the last K levels, wherein M=N+K, and N≤M / 2.

[0029] As can be seen, the waveguide layer of this off-chip light-emitting device primarily consists of an M-level concentric semicircular grating and a waveguide. Both the upper and lower cladding layers of the device are SiO2, with a metal mirror embedded in the lower cladding. The primary function of this off-chip light-emitting device is to emit on-chip light into a spatial region. Light enters the M-level concentric semicircular grating region from the waveguide, then passes through the M-level shallowly etched grating before being emitted vertically. Some light that leaks into the substrate is reflected by the metal mirror and emitted from above the grating. A specific example is provided below to further illustrate the present invention.

[0030] The waveguide layer of the off-chip light emitting device of this embodiment also includes a narrow waveguide structure 8, which is located between the waveguide 6 and the M-level concentric semicircular grating 7 and is perpendicular to the waveguide 6. By setting the narrow waveguide structure 8, the end face reflection can be reduced, thereby reducing the loss.

[0031] The structural parameters of the off-chip light emitting device of this embodiment are shown in Table 1, where H and hu are the thickness of the waveguide compatible with CMOS and the thickness of the upper cladding layer of the device, respectively. Therefore, H = 0.22 μm, h u =3μm. Figure 2 The mark A in the figure is a shallow etched groove, which is designed to facilitate the device to emit light vertically. The width W of the narrow waveguide structure in this embodiment is bar Smaller than the waveguide width W g , which can reduce the end face reflection and thus reduce the loss. In order to reduce the loss caused by the sudden change of the end face, the radius R0 of the first level circle of the concentric semicircular grating in this embodiment is designed to be the width W of the waveguide g The metal mirror in this embodiment is an Au reflector. When designing, it is necessary to make the optical path difference between the two beams of light be able to enhance the coherence of the two beams of light. Therefore, in this embodiment, the reflector depth h that controls the optical path difference is d is 1.0 μm, the thickness of the Au reflector is t m In this embodiment, the width a of the slits of each level of the concentric semicircular grating is the same, and the spacing b of the slits of each level is the same.

[0032] Table 1 Structural parameters of off-chip light emitting devices (unit: μm)

[0033] <![CDATA[W g ]]> <![CDATA[W bar ]]> <![CDATA[R0]]> a b 0.5 0.2 0.25 0.53 0.26 <![CDATA[h u ]]> h <![CDATA[h d ]]> H <![CDATA[t m ]]> 1.2 0.09 1 0.22 0.1

[0034] The wavelength dependence of this embodiment is simulated. For the convenience of representation, the mode field distribution of the device is shown as follows when the wavelength is 1.55 μm and TE0 is input: Figure 4 As shown in the figure, (a) is a top-down perspective, which clearly shows the mode field distribution of the semicircular grating structure. The mode field is basically fixed in the semicircular grating part and then emitted; (b) is a side-view perspective. The distribution of the mode field more intuitively reflects that the light is localized in the semicircular grating part and then vertically emitted to the upper cladding. Some of the light that leaks to the lower substrate is reflected to the upper cladding by the reflector, and very little light passes through the semicircular grating. Figure 5 and Figure 6 These are the emission far-field diagram and antenna pattern of the device of this embodiment, respectively. It can be clearly seen from these two figures that in the monitor with a height of 1 μm, the light field distribution is very concentrated, and the spatial emission solid angle is approximately within 30°.

[0035] Figure 7This is a graph showing the emission efficiency of this embodiment as a function of wavelength. It can be seen that within the wavelength range of 1.16μm to 1.61μm, the vertical emission efficiency of the device reaches 0.64 and above. The 450nm bandwidth covers the O-band, E-band, S-band, and C-band, which makes the device more suitable for future wide-bandwidth applications. At the same time, a full-etch simulation design was performed on the device. Figure 8 C is the curve of this embodiment, and D is the curve of the fully etched device. Figure 8 It can be clearly seen that the emission efficiency of the device of this embodiment in the wavelength range of 1.16 μm to 1.61 μm is significantly better than that of the fully etched device.

[0036] It is not difficult to find that the present invention uses a multi-level concentric semicircular grating, and the first several levels of the grating are designed as shallow etched grooves. This design can facilitate the vertical emission of light, and a narrow waveguide structure is set between the multi-level concentric semicircular grating and the single-mode waveguide. The narrow waveguide structure reduces end face reflection and thus reduces loss. In order to further reduce the loss caused by the sudden change of the end face, the radius of the first level circle of the semicircular grating is designed to be half the width of the single-mode waveguide. The off-chip light emitting device of the present invention can achieve a vertical emission efficiency of more than 0.64 in the wavelength range of 1.16μm to 1.61μm, and the bandwidth covers multiple bands, making the device better for future wide bandwidth applications.

Claims

1. An off-chip light emitting device, characterized in that: include: substrate; a lower cladding layer, located on the upper surface of the substrate and having a metal mirror embedded therein; a waveguide layer, located on the upper surface of the lower cladding, comprising a waveguide and an M-level concentric semicircular grating; an upper cladding layer, located on an upper surface of the waveguide layer; The waveguide is used to guide light into the M-level concentric semicircular grating; the metal mirror is used to reflect light leaking into the substrate to the M-level concentric semicircular grating; the M-level concentric semicircular grating is used to emit the received light in a vertical direction; the etching depth of the slits of the first N levels of the M-level concentric semicircular grating is less than the etching depth of the slits of the last K levels, wherein M=N+K, and N≤M / 2; The waveguide layer further includes a narrow waveguide structure, which is located between the waveguide and the M-level concentric semicircular grating and is perpendicular to the waveguide; the radius of the first-level circle of the M-level concentric semicircular grating is half the width of the waveguide.

2. The off-chip light emitting device according to claim 1, wherein: The width of the narrow waveguide structure is smaller than the width of the waveguide.

3. The off-chip light emitting device according to claim 1, wherein: The thickness of the metal mirror is 1 / 10 of the distance between the metal mirror and the waveguide layer.

4. The off-chip light emitting device according to claim 1, wherein: The width of the slits of each level of the M-level concentric semicircular grating is the same, and the spacing between the slits of each level is the same.

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