TWI531824B - Light receiving device - Google Patents

Description

Light receiving device

The present invention relates to a light collecting device, and more particularly to a light receiving device.

The fiber optical communication module is composed of a fiber optical transceiver module and a circuit module, wherein the fiber transmission module usually includes an optical transmission device (light Transmitting device) and a light receiving device. Optical fiber communication has the advantages of fast transmission speed, high capacity, low distortion, etc., and can effectively cope with the signal transmission of large-scale high-resolution images in the future. Optical fiber communication can be applied to long-distance signal transmission, such as submarine optical fiber cable, and can also be applied to short-distance local side signal transmission. Since the bandwidth of optical fiber communication is hundreds of times more than that of traditional cable communication, and the technology of optical fiber communication is still breaking through, the future of optical fiber network still has considerable growth, so some people say that the 21st century is the century of light.

In order to further increase the signal transmission capacity of the optical fiber, Wavelength Division Multiplex (WDM) technology is often used to enable multiple optical signals having different wavelengths to be simultaneously transmitted in one optical fiber to improve the overall information transmission amount. However, once the number of wavelengths increases, the width of each wavelength and the spacing of the center wavelength, the overall optical power, the cross-talk, and the maximum range over which the fiber can be transmitted must be considered. The most commonly used techniques for making a split-wave multiplexer are: (1) Thin Film Filter (TFF), (2) Array Waveguide Grating (AWG), and (3) Fiber Bragg (Fiber Bragg) Grating, FBG). Due to the above-mentioned split-wave multiplexer, the transmission distance is limited, and the working wavelength of the optical signal is mostly between 1475 and 1625 nm, so as to increase the transmittance of light and reduce transmission loss, but the relative cost is also relatively low. High, can not be mass produced in a low-cost semiconductor process.

In addition, in the spectroscopic technique, a known technique is used to fabricate a concave grating on the Rowland circle, so that the diffracted light generated by the incident light source is focused on the Loren circle to improve the conventional planar grating. (planar grating) requires two concave mirrors to make the light focus space and improve the grating splitting efficiency. In addition, the concave grating combines the functions of grating spectroscopic and concave mirror imaging. If the incident light source contains many different wavelengths of optical signals, the reflected light waves will reflect the different wavelengths of the optical signals to different angles due to the interference. The effect of splitting, which in turn reduces energy loss, and the space it takes up, replaces the traditional large monochromator.

The present invention relates to a light receiving device that reflects light signals of different wavelengths to a receiving portion at different positions by a reflection type diffraction grating to perform multi-channel spectroscopic processing. Since the reflective diffraction grating is a spectral component fabricated by a semiconductor process technology, it has the advantages of low insertion loss, low crosstalk, and easy mass production, so the channel number and bandwith of the light receiving device can be increased. And significantly reduce the cost of production.

According to an aspect of the invention, a light receiving device includes an input portion, a reflective diffraction grating, and a plurality of receiving portions. The input unit is configured to input a plurality of optical signals of different wavelengths. The reflective diffraction grating is located at one of the outlets of the input. The reflective diffraction grating includes a curved profile and a plurality of diffraction structures. The diffraction structures are disposed on the curved surface contour to separate optical signals of different wavelengths and focus the optical signals on a predetermined output surface. The diffractive structures are disposed between the contour points with a plurality of grating pitches. At least some of the grating spacings are different from each other. In addition, the plurality of receiving portions are disposed on the preset output surface for receiving the separated optical signals of different wavelengths.

In order to better understand the above and other aspects of the present invention, the preferred embodiments are described below, and in conjunction with the drawings, the detailed description is as follows:

The light receiving device of this embodiment separates and focuses the optical signals of different wavelengths on a predetermined output surface by using a reflective diffraction grating. The reflective diffraction grating combines the functions of splitting and focusing, thus replacing the collimator and focusing lens in traditional optical systems, thereby reducing the number of components used in optical systems and complex alignment problems. .

Please refer to FIG. 1 , FIG. 2 and FIG. 3 simultaneously. FIG. 1 is a schematic diagram of a light receiving device according to an embodiment, and FIG. 2 is a schematic diagram showing a diffraction principle of a reflective diffraction grating. The figure shows a schematic diagram of a reflective diffraction grating in accordance with an embodiment. The light receiving device 10 includes an input portion 12, a reflective diffraction grating 14, and a plurality of receiving portions 16. The input unit 12 is configured to input a plurality of optical signals L1 to Ln of different wavelengths. The reflective diffraction grating 14 is located at one of the outlets 121 of the input portion 12. The reflective diffraction grating 14 includes a curved profile 142 and a plurality of diffraction structures 144. The curved surface contour 142 has a plurality of contour points P ₀ ~ Pn. The diffraction structures 144 are disposed on the curved surface contour 142 for separating the optical signals L1 L Ln of different wavelengths and focusing the optical signals on a predetermined output surface 162 . The diffractive structures 144 are disposed between the contour points P ₀ -Pn at a plurality of grating pitches. At least some of the grating spacings are different from each other. In addition, the plurality of receiving portions 16 are disposed on the preset output surface 162 for receiving the separated optical signals L1 L Ln of different wavelengths.

In an embodiment, the receiving portion 16 is, for example, a photoelectric converter composed of a group of photoelectric elements, such as photodiodes, which are sequentially arranged in parallel on the preset output surface 162 to different wavelengths. The optical signals L1~Ln are converted into a set of electrical signals. At least some of the spacings between the receiving portions 16 are different from each other, and the position of the receiving portion 16 is related to the grating spacing setting, and can be adjusted according to the actual design, so that the receiving portions 16 are non-equally arranged on the preset output surface. 162. The number of receiving sections 16 is not limited, and the looking-up input section 12 may allow transmission of the maximum number of optical signals. In addition, the receiving portion 16 can also be a set of optical fibers or a hybrid receiver in which optical fibers and optoelectronic components are combined. After each optical fiber is divided into optical signals of a single wavelength, data processing is performed by the subsequent photoelectric components, but the optical signals of the single wavelength can be directly transmitted again without photoelectric conversion.

In an embodiment, the input portion 12 is, for example, an optical fiber having an outlet 121 at its end. The optical signals L1~Ln of different wavelengths can be transmitted inside the optical fiber at the same time without mutual interference, so that the signal transmission amount and the bandwidth are relatively increased. In one embodiment, the available wavelengths of the optical signals L1 L Ln are in the range of 600 to 800 nm, and the number thereof is at least 3 or more. If the resolution of the light receiving device 10 to the optical signals L1 to Ln is higher, the number of available frequency bands is also higher. For example, when the available bandwidth is 200 nm and the minimum resolution is 5 nanometers (nm), one fiber can simultaneously transmit 40 different wavelengths of optical signals L1~Ln. If the transmission speed is 10 Gbps, the amount of data that can be transmitted in one second is about 400 Gb, which is equivalent to the capacity of a Blu-ray disc. Therefore, replacing the traditional cable with an optical fiber can overcome the limitation of the conventional cable bandwidth and reduce the noise interference of the electromagnetic wave. It can be seen that the light receiving device of the present invention can be applied to a module using an optical fiber as a transmission interface, for example, a fiber optic transmission module connected between a computer and its peripheral electronic devices, or a server connected to a local area network, printed A fiber optic transmission module between the watch machine, the photocopier and the terminal computer to greatly increase the amount of data transmitted.

The diffraction principle of Fig. 2 and the diffraction structure 144 of the reflection type diffraction grating 14 of Fig. 3 will be described below. For convenience of description, the shape of the diffraction structure 144 illustrated in FIG. 3 is illustrated by a similar triangle. The diffraction structure 144 is disposed between the contour points P ₀ to Pn at a plurality of grating pitches. At least some of the grating pitches are different from each other such that the optical signals L1 L Ln of different wavelengths are directed to the preset output surface 162 in a manner substantially perpendicular to the preset output surface 162 . The number of mutually different grating pitches can be adjusted according to the actual design. For convenience of explanation, FIG. 3 only illustrates three different grating spacings d ₀ , d ₁ and d ₂ . In one embodiment, the grating pitches d ₀ , d _{1 ,} and d ₂ are the lengths of the line segments from the contour points P ₀ to P ₁ , P ₁ to P ₂ , and P ₂ to P ₃ , respectively.

In Figures 2 and 3, the central contour point P ₀ is the center point of the curved contour 142, and the reference point (preferably the contour point P ₁ ) is the next contour point temporarily selected during the optical simulation and adjustment process, when a single When the wavelength ray is emitted from a known incident angle α to a region grating with a line segment length d ₀ connecting P ₀ and P ₁ as a grating pitch, the focus position on the preset output surface 162 after diffraction may be combined with The ideal focus has an aberration Δy' (aberration). The aberration Δy' can be passed through the following grating equation (Grating Equation)

Sinα+sinβ= Abbreviated induced spectral resolution Δ λ _A =

Wherein, the grating pitch d ₀ is the grating pitch of the regional grating P ₁ P ₀ ; the diffraction angle β is the angle of the assumed single-wavelength ray A1 after being circulated by the regional grating P ₁ P ₀ , which is a function of λ; It is the wavelength of A1; m is the diffraction order; the distance of the diffracted ray whose distance r' is A1 is diffracted by the area grating P ₁ P ₀ to the preset output surface 162. Under the premise that the grating spacing d ₀ , the diffraction angle β, the wavelength λ, the diffraction order m and the distance r′ are known, the value of each aberration Δy′ can be solved by the grating formula to find the corresponding aberration analysis. Degree Δ λ _A . Thus, the position of the contour point on the curved contour 142 of the reflective diffraction grating 14 can be determined from the central contour point P ₀ as a reference point, and the grating spacing and the local grating profile are repeatedly adjusted by optical simulation to find out _A position point at which the aberration resolution Δ λ _{A is} smaller than a predetermined value is taken as a position of the preferred second contour point P ₁ , and then the contour point P ₁ is used as a reference point, and the grating pitch and the area are repeatedly adjusted by the same optical simulation. The grating profile is searched for a position where the aberration resolution Δ λ _{A is} smaller than a predetermined value as the position of the contour point P ₂ which is preferably one more, and thus repeated until the curved contour 142 of the reflective diffraction grating 14 is separated by a different grating pitch. The region of the grating profile is full, and the thus obtained reflective diffraction grating 14 will be a preferred grating which can be obtained by optical simulation.

Compared with the conventional concave grating with a fixed grating pitch, it is almost impossible to form a vertical or nearly vertical intersection between the diffracted light and the focused circular arc on the Roland circle, which is not practical. In contrast, the present invention finds the non-fixed grating pitch and the non-circular surface curved contour 142 by optical simulation, so that the diffracted light can be directed to the preset output surface 162 substantially perpendicular to the preset output surface 162. Not only the diffraction efficiency is better, but the preset output surface 162 does not have to be an arc on the Roland circle which is difficult to implement, but may be another output surface that is easy to implement, such as a straight line on a plane, such a reflection type. The diffraction grating 14 will have a very high value in practical applications.

The reflective diffraction grating 14 of the present invention has a non-planar curved contour 142 (for example, a three-dimensional spherical surface or a curved surface) and unequal grating spacing, and is conventionally carved on a flat metal or glass surface with a precision diamond knife. The method of refracting the structure 144 becomes unsuitable for at least the reason that the diamond knives are difficult to change the pitch and the surface of the non-planar material is difficult to operate. Therefore, the reflective diffraction grating 14 of the present invention is more suitable for the process. The material is selected by using a semiconductor substrate material (such as germanium or III-V semiconductor material) to etch a non-planar diffraction structure 144 on the vertical surface of the wafer by etching, and then from the wafer. Cut it out.

Please refer to FIG. 4 and FIG. 5 . FIG. 4 is an exploded perspective view of the light receiving device according to an embodiment, and FIG. 5 is a schematic view showing the light traveling in the optical channel of FIG. 4 . The light receiving device 10 further includes an upper waveguide plate 120, a lower waveguide plate 130, a first extinction element 150, and a second extinction element 160.

The lower waveguide plate 130 is disposed substantially parallel to the upper waveguide plate 120. The upper waveguide plate 120 has a first reflective surface 122, and the lower waveguide plate 130 has a second reflective surface 132 opposite the first reflective surface 122. The optical path 140 is formed between the first reflecting surface 122 and the second reflecting surface 132, so that the optical signals L1 to Ln from the input portion 12 travel in the optical channel 140 as shown in FIG. The optical channel 140 formed between the first reflective surface 122 and the second reflective surface 132 is generally of a cavity type, which is different from the principle of total reflection used for transmitting light in the optical fiber. In this embodiment, the optical signals L1~Ln are limited. Reflectively reflected between these reflective surfaces and forwarded, but can also be filled with appropriate media (such as glass, plastic, or acrylic) for the light signal to be reflected and forwarded while preventing dust or other pollution. The matter accumulates on the upper and lower waveguide plates to affect the flatness and reflectivity of the waveguide plate.

The upper waveguide plate 120 and the lower waveguide plate 130 must have good flatness and reflectivity, so that the optical signals L1 to Ln can achieve the lowest loss and the best when traveling between the upper waveguide plate 120 and the lower waveguide plate 130. The light source concentrates the effect. Therefore, the material of the upper waveguide plate 120 and the lower waveguide plate 130 is, for example, stainless steel, tantalum wafer, glass, optical disk or hard disk. In addition, if the material reflectance of the upper waveguide plate 120 and the lower waveguide plate 130 is less than the required standard, a high-reflection film may be disposed on the first reflective surface 122 and the second reflective surface 132 to solve the problem. Preferably, the material of the highly reflective film is an aluminum film.

In order to prevent oxidation, rust, roughness, etc. of the surfaces of the first reflective surface 122 and the second reflective surface 132 over time, the flatness and reflectivity of the surface of the reflective surface are reduced, and the first reflective surface 122 and the second reflective surface are A first protective film and a second protective film (not shown) are respectively disposed on the high reflective film of the surface 132. The material of the protective film is, for example, cerium oxide.

The light receiving device disclosed in the above embodiments of the present invention regulates the optical signals of different wavelengths input from the input unit to travel in the optical channel between the upper and lower waveguide plates, so that the optical signals are more concentrated and less likely to diverge. In combination with the jagged extinction element, the optical signal with too large incident angle is eliminated, thereby reducing the stray light reaching the receiving portion, so that the optical signal to be separated is not interfered by stray light, so as to obtain clearer signal quality. .

In conclusion, the present invention has been disclosed in the above preferred embodiments, and is not intended to limit the present invention. A person skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

10. . . Light receiving device

12. . . Input section

14. . . Reflective diffraction grating

16. . . Receiving department

L1~Ln. . . Optical signal

121. . . Export

142. . . Surface contour

144. . . Diffractive structure

P ₀ ~Pn. . . Outline point

162. . . Preset output face

d ₀ , d ₁ , d ₂ . . . Grating spacing

120. . . Upper waveguide plate

130. . . Lower waveguide plate

122. . . First reflecting surface

132. . . Second reflecting surface

140. . . Optical channel

150. . . First extinction element

160. . . Second extinction element

FIG. 1 is a schematic diagram of a light receiving device according to an embodiment.

Figure 2 is a schematic diagram showing the diffraction principle of a reflective diffraction grating.

FIG. 3 is a schematic diagram of a reflective diffraction grating according to an embodiment.

4 is an exploded perspective view of a light receiving device according to an embodiment.

Figure 5 is a schematic diagram showing the travel of light in the optical channel of Figure 4.

10. . . Light receiving device

12. . . Input section

14. . . Reflective diffraction grating

16. . . Receiving department

121. . . Export

142. . . Surface contour

162. . . Preset output face

L1~Ln. . . Optical signal

Claims (9)

A light receiving device is applied to optical fiber communication, the light receiving device includes: an input portion for inputting a plurality of optical signals of different wavelengths; and a reflective diffraction grating disposed at an exit of the input portion, the reflective type winding The grating includes: a curved surface contour having a plurality of contour points; and a plurality of diffraction structures disposed on the curved surface contour for separating the optical signals of the different wavelengths and focusing on a predetermined output surface, The diffraction structure is disposed between the contour points by a plurality of grating pitches, at least some of the grating pitches are different from each other; and a plurality of receiving portions are disposed on the preset output surface for receiving the separated The optical signals of different wavelengths, wherein at least some of the receiving portions are non-equidistantly arranged on the preset output surface. The light receiving device of claim 1, wherein the number of the optical signals of the different wavelengths is greater than 3. The light receiving device of claim 1, wherein the predetermined output surface is a straight line on a plane. The light receiving device of claim 1, wherein the curved profile and the diffraction structures are formed on a semiconductor substrate material. The light receiving device of claim 4, wherein The semiconductor substrate material is tantalum. The light receiving device of claim 1, further comprising: an upper waveguide plate having a first reflecting surface; and a lower waveguide plate disposed substantially parallel to the upper waveguide plate and having a second reflection The first reflective surface is opposite to the second reflective surface, and an optical channel is formed between the first reflective surface and the second reflective surface, so that the optical signals from the input portion are in the optical channel. Travel inside. The light receiving device of claim 6, further comprising a first matting element and a second extinction element disposed on opposite sides of the optical channel. The light receiving device of claim 1, wherein the receiving portions comprise a set of photovoltaic elements, a set of optical fibers, or a combination thereof. The light receiving device of claim 1, wherein the input portion comprises an optical fiber.