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EP-4736601-A1 - ULTRA-BROADBAND INFRARED EMITTER

EP4736601A1EP 4736601 A1EP4736601 A1EP 4736601A1EP-4736601-A1

Abstract

An illumination device, system, and method of fabricating the device are described. The device includes a light emitting diode (LED) structure having an LED that emits blue light. A phosphor layer of the LED structure partially absorbs a portion of the blue light and emits near infrared light. A plate that is separated from the LED structure absorbs the blue light and transmits the near infrared light. The plate heats up due to absorption of the blue light and emits blackbody radiation with a peak emission larger than the near infrared light. The plate is separated by an air gap or using a non-conductive layer. For a portable spectroscopic device, one or more sensors detect the emitted light impinging on a target.

Inventors

  • VAN VOORST VADER, PIETER JOHANNES QUINTUS
  • ROELING, Erik
  • PFEFFER, NICOLA BETTINA

Assignees

  • Lumileds LLC

Dates

Publication Date
20260506
Application Date
20240618

Claims (20)

  1. 1. An illumination device comprising: a light emitting diode (LED) structure configured to emit light in a first wavelength range; and a plate separated from the LED structure, the plate configured to absorb at least some of the light emitted by the LED structure and to emit blackbody radiation in a second wavelength range, the blackbody radiation caused by an elevated temperature of the plate from absorption of the light from the LED structure by the plate, the second wavelength range having a peak emission at a wavelength larger than the first wavelength range.
  2. 2. The illumination device of claim 1, wherein the LED structure includes: a semiconductor active region configured to emit blue light as the light of the first wavelength range; and a phosphor layer configured to absorb a portion of the blue light and to emit light in a third wavelength range between the first wavelength range and the second wavelength range.
  3. 3. The illumination device of claim 2, wherein the phosphor layer includes a sintered aluminum oxide (A12O3) layer with phosphor dopants.
  4. 4. The illumination device of claim 2 or 3, wherein the plate is substantially transparent to the light in the third wavelength range.
  5. 5. The illumination device of any of claims 1-4, wherein the plate comprises an infrared transparent filler that is configured to heat the plate in response to absorption of the light in the first wavelength range and to emit light in a mid-infrared range.
  6. 6. The illumination device of any of claims 1-5, wherein the plate includes at least one of doped silicon or undoped silicon that is configured to heat the plate in response to absorption of the light in the first wavelength range and to emit light in a mid-infrared range.
  7. 7. The illumination device of any of claims 1-6, further comprising non- conductive supports configured to separate the LED structure and the plate, the LED structure and the plate separated by an air gap between the non-conductive supports.
  8. 8. The illumination device of any of claims 1-7, further comprising a non- conductive layer configured to separate the LED structure and the plate.
  9. 9. The illumination device of any of claims 1-8, further comprising a lens having a first surface on which the plate is mounted, the light in the first wavelength range configured to impinge on a second surface of the lens that is opposite the first surface of the lens.
  10. 10. The illumination device of any of claims 1-9, wherein the plate comprises a first planar surface facing the LED structure and a second surface containing dimples that are at a different distance from the LED structure than a planar portion of the second surface.
  11. 11. The illumination device of any of claims 1-10, further comprising a dichromatic mirror, the dichromatic mirror being a structure disposed between the LED structure and the plate or being a coating on the plate, the dichromatic mirror transparent to the light in the first wavelength range and configured to reflect light in the second wavelength range back towards the plate.
  12. 12. The illumination device of any of claims 1-11, further comprising another LED structure configured to emit light in a third wavelength range between the first wavelength range and the peak emission of the second wavelength range, the plate configured to absorb a portion of the light emitted by the other LED structure and emit the blackbody radiation in the second wavelength range.
  13. 13. An electronic system comprising: an illumination device comprising: a light emitting diode (LED) structure configured to emit light in a first wavelength range; and a plate separated from the LED structure, the plate configured to absorb at least some of the light emitted by the LED structure and to emit blackbody radiation in a second wavelength range, the blackbody radiation caused by an elevated temperature of the plate from absorption of the light from the LED structure by the plate, the second wavelength range having a peak emission at a wavelength larger than the first wavelength range; and at least one sensor configured to detect light that is dependent on the light of the first wavelength range and the light of the second wavelength range emitted by the illumination device.
  14. 14. The electronic system of claim 13, wherein the plate comprises an infrared transparent filler that is configured to heat the plate in response to absorption of the light in the first wavelength range to emit light in a midinfrared range.
  15. 15. The electronic system of claim 13 or 14, further comprising at least one of: non-conductive supports configured to separate the LED structure and the plate, the LED structure and the plate separated by an air gap between the non-conductive support, or a non-conductive layer configured to separate the LED structure and the plate.
  16. 16. The electronic system of claim 15, further comprising: a printed circuit board (PCB) on which the LED structure and the at least one sensor are mounted; and a controller mounted on the PCB, the controller configured to control a pump intensity of the LED structure to control heating of the plate and emission of the light of the second wavelength range.
  17. 17. The electronic system of any of claims 13-16, wherein: the electronic system is a portable spectroscopic device, and the electronic system further includes a processor configured to at least one of provide an element analysis of a sample illuminated by the illumination device based on an output of the at least one sensor, or determine a concentration of at least one gas based on an output of the at least one sensor.
  18. 18. The electronic system of any of claims 13-17, wherein the plate comprises a first planar surface facing the LED structure and a second surface containing dimples that are at a different distance from the LED structure than a planar portion of the second surface.
  19. 19. A method of fabricating an electronic device, the method comprising: disposing a light emitting diode (LED) structure on a mounting structure; positioning a plate to be separated from the LED structure such that, during operation, the LED structure generates light in a first wavelength range that is partially absorbed by the plate, which heats up to an elevated temperature and emits blackbody radiation in a second wavelength range caused by heating the plate to the elevated temperature, the second wavelength range having a peak emission greater than the first wavelength range; and disposing at least one sensor to detect light that is dependent on the light of the first wavelength range and the light of the second wavelength range emitted by the electronic device.
  20. 20. The method of claim 19, further comprising detecting the light of the second wavelength range emitted by the electronic device during at least one of heating and cooling of the plate in response, a peak emission shifting in time dependent on the heating and cooling of the plate.

Description

ULTRA-BROADBAND INFRARED EMITTER PRIORITY CLAIM [0001] This application claims the benefit of priority to United States Provisional Patent Application Serial No. 63/523,480, filed June 27, 2023, which is incorporated herein by reference in its entirety. FIELD OF THE DISCLOSURE [0002] The present disclosure relates to light emitting diode (LED) structures. In particular, embodiments are directed to LED structures that emit in both the visible and infrared (IR) ranges. BACKGROUND OF THE DISCLOSURE [0003] Light emitters are used in a wide variety of applications. For example, the use of solid state light emitters in spectroscopy -based applications has been of increasing interest due to the portability and relatively low cost. Despite this, cost and size issues, among others, still abound for such devices as multiple different emitters in different wavelengths may be incorporated into such devices to provide a desired emission range to enable detection of multifarious materials. BRIEF DESCRIPTION OF THE DRAWINGS [0004] FIG. 1 shows an example apparatus, in accordance with some examples. [0005] FIG. 2 illustrates an example of a general device in accordance with some embodiments. [0006] FIG. 3 illustrates an example LED array, in accordance with some examples. [0007] FIG. 4 illustrates a cross-section of a single LED from an LED array, in accordance with some examples. [0008] FIG. 5 illustrates a cross-sectional view of a single-die package architecture, in accordance with some examples. [0009] FIG. 6A illustrates an example spectrum emitted by the lightconverting layer, according to some embodiments. [0010] FIGS. 6B-6E illustrate example spectrums emitted by the apparatus, according to some embodiments. [0011] FIGS. 7A-7D illustrate example lighting structures according to some embodiments. [0012] FIG. 8 illustrates an example system, according to some embodiments. [0013] FIG. 9 illustrates a top plan view of an example array suitable for implementing embodiments described herein. [0014] FIG. 10 illustrates an example method of fabricating an illumination device, according to some embodiments. DETAILED DESCRIPTION [0015] Material spectroscopy may use one or more light sources covering a diverse wavelength range. In some examples, such wavelength ranges may generally include light in the near- and mid-IR range, respectively about 0.8 pm to about 2.5 pm and up to about 8 pm. LEDs may be preferred as light sources in mobile devices because of the small dimensions of the LEDs. Solid state IR sources mostly emit in the wavelength range between about 0.8 pm and about 2.5 pm. The solid state IR sources include direct emitters and phosphor-converted emitters. [0016] A phosphor-converted emitter may include an LED that emits light having a shorter (e.g., blue) wavelength, which then pumps a thin layer of a photon-converting material on the LED. The photon-converting material converts the blue photons from the LED to photons with a mostly lower wavelength. With phosphor conversion, wavelengths of up to about 2.5 pm may be produced. The phosphor can be dispersed in an organic carrier (such as Silicone rubber) or a ceramic carrier, such as A12O3. [0017] In addition, a limited portion of the blue light produced by the LED is converted, with the excess being emitted as the blue light or dissipated via heat. The heat limits for dissipation may be dependent on the material; organic-based carrier materials may be able to withstand temperatures up to about 300 to about 350 degrees C without damage, while inorganic carriers may be able to withstand much higher temperatures (up to several thousand degrees C). [0018] For spectroscopy applications, for example, mobile spectroscopy applications it may be desirable to use IR wavelengths up to 10 pm. In general, IR radiation is emitted by an object when above absolute zero (0 Kelvin). A perfect emitter is a “black body”, having a dominant wavelength described by Wien’s law, which is approximately 2898 pm /T(K). At room temperature (293 K), the wavelength emitted is about 10 pm. Using Wien’s law, to emit a peak wavelength of about 2.5 pm an object is heated to about 900°C by direct heating. Thus, the peak wavelength may shift with temperature change, which may be used in embodiments in which not only may a steady-state peak wavelength allow the object to act as a radiation source, but in addition use the object as a radiation source during heating up and/or cooling down of the object. [0019] FIG. 1 shows an example apparatus 100, in accordance with some examples. In some embodiments, other components may be present, while in other embodiments not all of the components may be present. The apparatus 100 may be, for example, a smart phone or portable spectroscopic device. The apparatus 100 may include both a light source 110 and a sensor 120. The sensor 120 may detect radiation associated with a target 104, such as one or more gases. A processor 130 may be used to control various func