Systems and methods for particle detection

• US 9,012,830 B2
• Filed: 04/30/2012
• Issued: 04/21/2015
• Est. Priority Date: 12/11/2009
• Status: Active Grant

• Current Assignee: Washington University In St Louis
• Original Assignee: Washington University In St Louis
• Inventors: Zhu, Jiangang, Ozdemir, Sahin Kaya, Yang, Lan
• Primary Examiner(s): LEE, JOHN R
• Application Number:
  US13/460,170
• Publication Number:
  US 20120268731A1
• Time in Patent Office: 1,086 Days
• Field of Search: 250/216, 250/227.11, 250/227.14, 250/227.18, 250/227.23, 356/300, 356/301, 356/319, 356/320, 356/335, 356/336, 977/840, 977/880, 977/881, 385/12
• US Class Current: 250/227.14
• CPC Class Codes: B82Y 35/00 Methods or apparatus for measurement or analysis of nanostructures
• CPC Class Codes: G01N 21/7746 the waveguide coupled to a cavity resonator
• CPC Class Codes: Y10S 977/88 with arrangement, process, or apparatus for testing

Abstract

A particle detection system is provided. The particle detection system includes at least one tapered optical fiber, a light source configured to transmit light through the at least one tapered optical fiber, a photodetector configured to measure a characteristic of the light being transmitted through the at least one optical fiber, and a computing device coupled to the photodetector and configured to determine whether a nanoparticle is present within an evanescent field of the at least one tapered optical fiber based on the measured light characteristic.

Claims

1. A particle detection system comprising:

at least one tapered optical fiber;

a light source configured to transmit light through said at least one tapered optical fiber;

a photodetector configured to measure a transmitted power of the light being transmitted through said at least one optical fiber; and

a computing device coupled to said photodetector and configured to determine, without coupling said at least one tapered optical fiber to a resonator, whether a nanoparticle is present within an evanescent field of said at least one tapered optical fiber based on a discrete jump in the transmitted power of the light.

2. A particle detection system according to claim 1, wherein said at least one tapered optical fiber comprises:

a first normal portion having a first diameter;

a narrow portion having a second diameter smaller than the first diameter, wherein the evanescent field surrounds at least a portion of said narrow portion;

a second normal portion having the first diameter;

a first tapered portion extending between said first normal portion and said narrow portion; and

a second tapered portion extending between said narrow portion and said second normal portion.

3. A particle detection system according to claim 2, wherein the second diameter of said narrow portion is approximately 8 micrometers.

4. A particle detection system according to claim 1, wherein said computing device is further configured to estimate a size of the nanoparticle based on a height of the discrete jump.

5. A particle detection system according to claim 1, wherein said computing device is further configured to determine a number of nanoparticles in the evanescent field based on a number of discrete jumps in the transmitted power of the light.

6. A particle detection system according to claim 1, wherein said at least one tapered optical fiber comprises:

a first tapered optical fiber forming a first leg of an interferometer; and

a second tapered optical fiber optical fiber forming a second leg of the interferometer, wherein said computing device is configured to determine a phase difference between light being transmitted through said first tapered optical fiber and light being transmitted through said second tapered optical fiber.

15. A particle detection system according to claim 1, wherein a height of the discrete jump represents an effective scattering loss due to the nanoparticle.

16. A particle detection system according to claim 1, wherein the discrete jump indicates a binding of the nanoparticle to said at least one tapered optical fiber.

17. A particle detection system according to claim 2, wherein a height of the discrete jump varies with a position of the nanoparticle along said narrow portion.

18. A particle detection system according to claim 1, wherein the discrete jump is a loss in the transmitted power.

7. A method for detecting nanoparticles, said method comprising:

transmitting light through a tapered optical fiber;

measuring a transmitted power of the light being transmitted through the tapered optical fiber; and

determining, without coupling the tapered optical fiber to a resonator, whether a nanoparticle is present within an evanescent field of the tapered optical fiber based on a discrete jump in the transmitted power of the light.

8. A method according to claim 7, wherein transmitting light though a tapered optical fiber comprises transmitting light through the tapered optical fiber such that the light adiabatically transforms between a core mode and a cladding mode as it propagates through the tapered optical fiber.

9. A method according to claim 7, further comprising estimating a size of the nanoparticle based on a height of the discrete jump.

10. A particle detection system according to claim 7, further comprising determining a number of nanoparticles present in the evanescent field based on a number of discrete jumps in the transmitted power of the light.

11. A method of assembling a particle detector, said method comprising:

coupling a tapered optical fiber to a light source, the light source being configured to transmit light through the tapered optical fiber;

coupling a photodetector to the tapered optical fiber, the photodetector being configured to measure a transmitted power of the light being transmitted through the tapered optical fiber; and

coupling a computing device to the photodetector, the computing device being configured to determine, without coupling the tapered optical fiber to a resonator, whether nanoparticles are present within an evanescent field of the tapered optical fiber based on a discrete jump in the transmitted power of the light.

12. A method according to claim 11, wherein coupling a tapered optical fiber comprises coupling a tapered optical fiber including a first normal portion having a first diameter, a narrow portion having a second diameter smaller than the first diameter, a second normal portion having the first diameter, a first tapered portion extending between the first normal portion and the narrow portion, and a second tapered portion extending between the narrow portion and the second normal portion, wherein the evanescent field surrounds at least a portion of the narrow portion.

13. A method according to claim 11, wherein coupling a computing device comprises coupling a computing device configured to estimate a size of a nanoparticle based on a height of a discrete jump in the transmitted power of the light.

14. A method according to claim 11, wherein coupling a computing device comprises coupling a computing device configured to determine a number of nanoparticles based on a number of the discrete jumps in the transmitted power of the light.