PCSEL for glucose monitoring
By using PCSEL in the range of 2.0-2.4 μm, the existing glucose monitoring system has been solved, and high beam quality and low cost non-invasive glucose monitoring are achieved.
Patent Information
- Application Number
- CN202411114944.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-06-11
- Filing Date
- 2024-08-14
- Publication Date
- 2025-02-21
AI Technical Summary
The existing glucose monitoring system is highly invasive, has low laser beam quality, has difficulty in tuning wavelengths, and is costly, making it difficult to meet the needs of compact wearable sensors.
Non-invasive glucose monitoring is performed using a photonic crystal surface emitting laser (PCSEL) in the range of 2.0-2.4μm. High beam purity and beam quality are achieved through photonic lattice design, and single-chip integration of multiple wavelengths is supported.
Achieve high beam quality and low spectral bandwidth, support monolithic integration of multiple wavelengths, reducing system cost and complexity, and is suitable for compact wearable glucose sensor applications.
Smart Images
Figure CN119492708A_ABST
Abstract
Description
[0001] Citations of Related Applications
[0002] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 519,805, filed on August 15, 2023, entitled “PCSEL FOR GLUCOSE MONITORING,” the disclosure of which is incorporated herein by reference in its entirety. Technical Field
[0003] A PCSEL for glucose monitoring is disclosed. Background Art
[0004] The limitations and disadvantages of conventional systems and methods for glucose monitoring will become apparent to those skilled in the art by comparing such methods with certain aspects of the present methods and systems provided in the remainder of this disclosure with reference to the accompanying figures. Summary of the invention
[0005] The systems and methods disclosed herein monitor glucose using a Photonic Crystal Surface-Emitting Laser (PCSEL) substantially as shown in and / or described in connection with at least one of the accompanying drawings, as more fully provided in the claims. BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Figure 1 A first exemplary top emitter structure having a PCSEL according to various exemplary embodiments of the present disclosure is shown.
[0007] Figure 2 An exemplary bottom emitter structure with a PCSEL according to various exemplary embodiments of the present disclosure is shown.
[0008] Figure 3 A second exemplary top emitter structure with a PCSEL according to various exemplary embodiments of the present disclosure is shown.
[0009] Figure 4 A third exemplary top emitter structure with a PCSEL according to various exemplary embodiments of the present disclosure is shown.
[0010] Figure 5An exemplary structure of two monolithic arrays having different wavelength ranges co-integrated on the same substrate according to various exemplary embodiments of the present disclosure is shown. DETAILED DESCRIPTION
[0011] Millions of people suffer from diabetes and need to monitor glucose levels multiple times a day. However, the monitoring systems available today are invasive. Although today's monitoring systems can use lasers, these systems are not adequate. For example, known existing solutions using 2.0-2.4μm laser sources include bulk lasers (such as excimer lasers) that are not suitable for compact wearable glucose sensor applications. Another existing solution includes a distributed feedback laser (DFB). In glucose level monitoring applications using DFB lasers, the epi stack for each wavelength is different, and the DFB lasers must be integrated on the same platform. This integration limits the number of wavelengths that can be used with high yield, which also makes this solution expensive. In addition, existing solutions have a relatively wide spectral bandwidth (SBW) and low beam quality (e.g., M for each wavelength (e.g., ~1nm). 2 >1.1). Although tunable lasers are also compatible with 2.0-2.4 μm range emission, precise wavelength tuning of the laser is very difficult.
[0012] The present disclosure describes non-invasive systems and methods for monitoring glucose. As described below, according to various exemplary embodiments of the present disclosure, 2.0-2.4 μm photonic crystal surface emitting lasers (PCSELs) can be used for non-invasive glucose monitoring and other medical optical sensing applications. PCSELs provide excellent beam purity and excellent beam quality for such optical sensing applications. In addition, PCSELs enable monolithic integration of wavelength ranges that may be required for absorption-based glucose sensing applications.
[0013] The emission wavelength of PCSEL is defined by the photonic lattice design and can be limited by the etching tool capabilities. The wavelength accuracy is significantly better than existing solutions. PCSEL has significantly lower SBW (e.g., <0.1nm) and excellent beam quality (e.g., M 2 <1.1). PCSELs enable monolithic integration of a larger number of wavelengths. Therefore, a single epi design can be used for multiple wavelengths.
[0014] Although the present disclosure describes glucose monitoring using a monolithic PCSEL array using wavelengths between 2.0-2.4 μm, other wavelength ranges may also be supported by using different material sets for active regions. For example, for wavelengths between 2.0-2.4 μm, highly strained InGaAs and GaSb materials may be used for the active region because the gain of InGaAs and GaSb supports this wavelength range.
[0015] The PCSEL emission direction can be top ( Figure 1 , Figure 3 , Figure 4 and Figure 5 ) or bottom ( Figure 2 ), depending on the application requirements.
[0016] Figure 1 A first exemplary top emitter structure having a PCSEL according to various exemplary embodiments of the present disclosure is shown.
[0017] The photonic crystal (PC) lattices L1, L2...Ln are designed to output wavelengths λ1, λ2...λn, respectively. For large optical apertures (e.g., OA>30μm), horizontal modes may be confined by the lattice. The epi stack (above and / or below the PC) may include pn junctions.
[0018] Figure 2 An exemplary bottom emitter structure with a PCSEL according to various exemplary embodiments of the present disclosure is shown.
[0019] and Figure 1 The same as in the PC lattice L1, L2...Ln is designed to output wavelengths λ1, λ2...λn, respectively. For large optical apertures (e.g., OA>30μm), the horizontal mode may be limited by the lattice. The epi stack above the PC may include a top distributed Bragg reflector (DBR) that is 100% reflective. The epi stack below the PC may include a bottom DBR that is not fully reflective.
[0020] Figure 3 A second exemplary top emitter structure with a PCSEL according to various exemplary embodiments of the present disclosure is shown.
[0021] and Figure 1 and Figure 2 Similar to the embodiment, PC lattices L1, L2…Ln are designed to output wavelengths λ1, λ2…λn respectively. Figure 3 The horizontal modes in the lattice are limited by the edge lattice (Le). The edge lattice allows OA < 30μm. The edge lattice can also be used for Figure 2 A smaller hole in a bottom-firing configuration.
[0022] Figure 4 A third exemplary top emitter structure with a PCSEL according to various exemplary embodiments of the present disclosure is shown.
[0023] and Figure 1-Figure 3 Similarly, PC lattices L1, L2...Ln are designed to output wavelengths λ1, λ2...λn respectively. Figure 4 Optical elements (OE1, OE2, ..., OEn) are added in. The optical elements may include lenses and / or diffusers that may be placed (eg, etched, deposited) on the emitting surface for beam shaping purposes.
[0024] The horizontal modes in a PCSEL are confined by a photonic crystal if the optical aperture is large (>30 μm), or by a secondary (external) photonic crystal for smaller apertures (<30 μm). The photonic bandgap of the "external" photonic crystal is smaller, and so it acts as a reflector.
[0025] For GaSb in the active region, the epi stack for pn junction implementations consists of a GaAs substrate and a cladding layer. The photonic crystal layer may include GaAs or GaSb.
[0026] Vertical mirror stacks can include GaAs and AlGaAs mirrors covering the desired wavelength range. Due to lattice mismatch, GaSb active regions may require additional lattice matching layers or wafer bonding.
[0027] For schemes with strained InGaAs in the active region, regrowth can be used to form the photonic crystal and the epi layer above it.The epi stack of InGaAs in the active region can include an InP substrate and cladding, a reflector, and a GaInAsP photonic crystal.
[0028] For both GaSb and InGaAs solutions, at least two stacking configurations are possible. One possible configuration includes p on one side of the active region and n on the other side. Another configuration includes n on both sides of the active region and a tunnel junction (TJ) therebetween.
[0029] PCSEL arrays can be monolithically manufactured for a range of wavelengths. The wavelength range in each monolithic array can depend on the uniformity requirements. The power uniformity across wavelength depends on the gain peak of the active region material. The wavelength range may or may not cover the range between 2.0-2.4 μm. If the wavelength range does not cover the range between 2.0-2.4 μm, multiple monolithic arrays can be used for the full range.
[0030] The wavelength of each device in the array can be different and controlled by lithography (photonic crystal design). In this case, the lattice constant will be different for each device.
[0031] The vertical mirror stack can be shared between all wavelengths or a subset of wavelengths, depending on the uniformity requirements. The overall response is a combination of the gain curve response and the mirror design, and this characteristic can be used to design a "flat" response and therefore have better uniformity.
[0032] Figure 5 An exemplary structure of co-integrating two monolithic arrays with different wavelength ranges on the same substrate according to various exemplary embodiments of the present disclosure is shown, wherein the PC lattices Ln+1, Ln+2...Lm are designed to output wavelengths λn+1, λn+2...λm, respectively.
[0033] Multiple monolithic arrays can be integrated on the same platform by, for example, a pick and place process. Each monolithic array can have an individually optimized DBR stack. Due to the low spectral bandwidth and high center wavelength design accuracy of PCSELs, the achievable wavelength spacing can be <5nm.
[0034] The wavelengths can also be spaced apart with temperature. The center wavelength of each device can have the same thermal shift. The refractive index can change with temperature. For example, for every degree Celsius, the refractive index can change by 0.07nm. The relative wavelength spacing can be maintained with temperature. Therefore, glucose monitoring applications using PCSELs may not require cooling. The wavelength spacing can depend on the etching capability.
[0035] The monitoring system can be compatible with integrated optics (i.e., deposited lenses and / or diffusers). The lasers in the array can be powered up simultaneously or sequentially. To support sequential wavelength scanning, each laser can have a separate metal contact and driver.
[0036] As used herein, the terms "circuit" and "circuitry" refer to physical electronic components (i.e., hardware) and any software and / or firmware ("code") that can configure, be executed by, and / or otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may include a first "circuit" when executing a first one or more lines of code, and may include a second "circuit" when executing a second one or more lines of code. As used herein, "and / or" refers to any one or more of the items in a list connected by "and / or". As an example, "x and / or y" refers to any element in a three-element set {(x), (y), (x, y)}. As another example, "x, y, and / or z" refers to any element in a seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. As used herein, the term "exemplary" refers to any element used as a non-limiting embodiment, example, or illustration. As used herein, the terms "for example" and "such as" list a list of one or more non-limiting embodiments, examples, or illustrations. As used herein, a circuit system is "operable" to perform a function whenever the circuit system includes the hardware and code (if necessary) required to perform the function, regardless of whether the performance of the function is disabled or not enabled (e.g., by a user-configurable setting, factory trim, etc.). As used herein, the term "based on" means "based at least in part on." For example, "x is based on y" means that "x" is based at least in part on "y" (and, for example, may also be based on z).
[0037] Although the inventive method and / or system has been described with reference to certain embodiments, it will be appreciated by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the inventive method and / or system. In addition, various modifications may be made to adapt specific circumstances or materials to the teachings of the present disclosure without departing from the scope of the present disclosure. Therefore, it is intended that the inventive method and / or system is not limited to the specific embodiments disclosed, but that the inventive method and / or system will include all embodiments falling within the scope of the appended claims.
Claims
1. A laser device, comprising: a first photonic crystal portion operable to outcouple light of a first wavelength in a vertical direction; as well as A second photonic crystal portion is operable to outcouple light of a second wavelength different from the first wavelength in the vertical direction.
2. The laser device according to claim 1, wherein: The first photonic crystal portion and the second photonic crystal portion are located on the same manufacturing layer.
3. The laser device according to claim 1, wherein: The laser device comprises: a first epitaxial layer operatively coupled below the first photonic crystal portion and the second photonic crystal portion, and A second epitaxial layer is operatively coupled over the first photonic crystal portion and the second photonic crystal portion.
4. The laser device according to claim 1, wherein: A glucose monitor includes the laser device.
5. The laser device according to claim 1, wherein: The laser device is a bottom emitting laser.
6. The laser device according to claim 1, wherein: The laser device is a top emitting laser.
7. The laser device according to claim 1, wherein: The first wavelength and the second wavelength are between 2.0 μm and 2.4 μm.
8. The laser device according to claim 1, wherein: One or more edge lattice portions adjacent to the first photonic crystal portion are operable to confine horizontal modes of the first wavelength, and One or more edge lattice portions adjacent the second photonic crystal portion are operable to confine horizontal modes of the second wavelength.
9. The laser device according to claim 1, wherein: The laser device comprises: One or more optical elements disposed on the emitting surface.
10. The laser device according to claim 1, wherein: The first wavelength and the second wavelength are determined according to temperature.
11. A method for manufacturing a laser device, comprising: fabricating a first photonic crystal portion operable to outcouple light of a first wavelength in a vertical direction; as well as A second photonic crystal portion is fabricated, the second photonic crystal portion being operable to outcouple light of a second wavelength different from the first wavelength in the vertical direction.
12. The method according to claim 11, wherein: The first photonic crystal portion and the second photonic crystal portion are located on the same manufacturing layer.
13. The method according to claim 11, wherein: The method comprises: Before manufacturing the first photonic crystal portion and the second photonic crystal portion, operatively manufacturing a first epitaxial layer, and A second epitaxial layer is fabricated on top of the first photonic crystal portion and the second photonic crystal portion.
14. The method according to claim 11, wherein: A glucose monitor includes the laser device.
15. The method according to claim 11, wherein: The laser device is a bottom emitting laser.
16. The method according to claim 11, wherein: The laser device is a top emitting laser.
17. The method according to claim 11, wherein: The first wavelength and the second wavelength are between 2.0 μm and 2.4 μm.
18. The method according to claim 11, wherein: The method comprises: one or more edge lattice portions fabricated adjacent to said first photonic crystal portion are operable to confine horizontal modes of said first wavelength, and One or more edge lattice portions fabricated adjacent to the second photonic crystal portion can be operated to confine horizontal modes of the second wavelength.
19. The method according to claim 11, wherein: The method comprises: One or more optical elements are positioned on the emitting surface.
20. The method of claim 11, wherein: The first wavelength and the second wavelength are determined according to temperature.