Ring-Geometry Photodetector Designs For High-Sensitivity And High-Speed Detection Of Optical Signals For Fiber Optic And Integrated Optoelectronic Devices

Abstract

A semiconductor photodetector comprising a closed loop configured to receive light from an external source adapted to trap light within said closed loop until absorption by the semiconductor.

Claims

1. A semiconductor photodetector comprising: a closed loop, said closed loop configured to receive light from an external source; and said closed loop adapted to trap light within said closed loop until absorption by the semiconductor.

2. The semiconductor photodetector of claim 1 wherein said closed loop recirculates light received from an external source.

3. The semiconductor photodetector of claim 1 wherein said closed loop recirculates light received from an external source until all light is absorbed by the semiconductor.

4. The semiconductor photodetector of claim 1 wherein said closed loop is a ring

5. The semiconductor photodetector of claim 1 wherein light is captured and re-circulated in the photodetector using a curved ridge-waveguide ring resonator.

6. The semiconductor photodetector of claim 1 wherein light is captured and re-circulated in the photodetector using straight waveguides and mirrors.

7. The semiconductor photodetector of claim 1 wherein light is captured and re-circulated in the photodetector using straight waveguides and mirrors, said waveguides and mirrors redirecting light into said closed loop.

8. The semiconductor photodetector of claim 1 wherein light is captured and re-circulated in the photodetector using a photonic crystal structure.

9. A method capturing light in a semiconductor photodetector comprising the following steps: directing light into a closed loop; and trapping light from an external source within said closed loop until absorption by the semiconductor.

10. The method of claim 9 further comprising the step of recirculating light received from an external source in said closed loop until absorption by the semiconductor.

11. The method of claim 10 wherein said light is recirculated until all light from an external source is absorbed by the semiconductor.

12. The method of claim 10 wherein said closed loop is a ring

13. The method of claim 10 wherein light is captured and re-circulated in the photodetector using a curved ridge-waveguide ring resonator.

14. The method of claim 10 wherein light is captured and re-circulated in the photodetector using straight waveguides and mirrors.

15. The method of claim 10 wherein light is captured and re-circulated in the photodetector using straight waveguides and mirrors, said waveguides and mirrors redirecting light into said closed loop.

16. The method of claim 10 using a photonic crystal structure.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0021] In the drawings, which are not necessarily drawn to scale, like numerals may describe substantially similar components throughout the several views. Like numerals having different letter suffixes may represent different instances of substantially similar components. The drawings illustrate generally, by way of example, but not by way of limitation, a detailed description of certain embodiments discussed in the present document.

[0022] FIG. 1A shows a waveguide bending photodetector design for an embodiment of the present invention.

[0023] FIG. 1B shows a total internal reflection mirrors photodetector design for an embodiment of the present invention.

[0024] FIG. 1C shows a photonic crystal design for an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed method, structure or system. Further, the terms and phrases used herein are not intended to be limiting, but rather to provide an understandable description of the invention.

[0026] As described above, there are fundamental limits in the physics of photodetectors that have forced trade-offs of either sensitivity or frequency response with current photodetector designs. In one aspect, the embodiments of the present invention concern designs that avoid these trade-offs by providing a compact, efficient and high-bandwidth ring photodetector. Preferred embodiments include three related photodetector designs using the total internal reflection waveguiding in FIG. 1a, the mirror reflection in FIG. 1b, or the photonic crystal guiding in FIG. 1c.

[0027] A common feature of the embodiments of the present invention is the entry point for light of that may be a whistle-geometry ring photodetector (WRP). A ridge waveguide 1a, 1b, as shown in FIGS. 1a and 1b, or a photonic crystal guiding structure 1c, as shown in FIG. 1c, collects light, either from an optical fiber, lens, or other part of a larger integrated optoelectronic device and guides it to the ring photodetector. The light is guided to a non-symmetrical Y-junction, which is shown in FIGS. 1a-1c as parts 2a, 2b and 2c, injecting the light into the absorptive part of the photodetector. The Y-junction allows the light to enter the unidirectional sections 3a, 3b and 3c which define a continuous path or ring such as a circle, rectangle, hexagonal as well as other designs such as oval, elliptical, and others, of the photodetector, where it can circulate until it is fully absorbed. The path of the light is shown as 4a, 4b, and 4c for the three embodiments shown in FIGS. 1a-1c. While the design in FIG. 1a re-circulates light by bending the waveguide, FIG. 1b uses strategically placed plurality of mirrors, labeled as 5b, to induce mirror reflection for keeping the light recirculating.

[0028] With the ring or continuous path designs of FIG. 1a-c, the absorptive depletion zone area may be engineered to be very thin in order to minimize drift time, and even though the absorption per unit length is low, the re-circulation of the light within the ring or continuous path means that all of the light will eventually be absorbed. The ring or continuous path can be made extremely small (1 μm in diameter or less), minimizing the area of the diode junction, which minimizes both the capacitance and the physical footprint for an integrated optoelectronic device for very large-scale integration (VLSI), where footprint size of devices is a limiting factor.

[0029] In other embodiments, unidirectional sections 3a, 3b and 3c define a ring or continuous path 4a-4c which are of a length that causes the light to re-circulate multiple times while the light is absorbed. These embodiments provide much more even illumination for the photodetector, minimizing optical nonlinear effects caused by the extremely small sizes used in the embodiments of the present invention.

[0030] While the foregoing written description enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The disclosure should therefore not be limited by the above described embodiments, methods, and examples, but by all embodiments and methods within the scope and spirit of the disclosure.