US 2025/0164626 A1Published application

Speed of light measurement using feedback of a pulsed laser

AssigneeKing Fahd University of Petroleum and Minerals

InventorAbdulaziz Mohammed Aljalal

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Abstract

Methods and systems for determining the speed of light by utilizing optical feedback from a laser diode include a laser diode mounted at a distance from a linear stage, with a beamsplitter positioned at an initial location along the stage. The laser diode generates a variably pulsed laser beam that is split by the beamsplitter into two portions. The first portion is reflected back to the laser diode, inducing stimulated amplification, while the second portion is detected by a photodetector. The photodetector measures the optical intensity and generates an amplified electrical signal. A data acquisition system records the frequency at which the laser power peaks, indicating resonance conditions. The beamsplitter is subsequently moved to a second position, and a new peak frequency is detected. Based on the measured frequencies and positions, the speed of light is calculated with high precision.

Claims20

Dependent claims

A method for determining the speed of light, comprising:

mounting, at a distance X0 from a linear stage, a laser diode;
mounting, at a first location X1 on the linear stage, a beamsplitter;
mounting a photodetector at a distance Xp from the beamsplitter, wherein the beamsplitter is located between the laser diode and the photodetector and a center of the beamsplitter is in line with an eye of the photodetector;
connecting the laser diode to a laser driver;
generating, by the laser driver, a current having a variable frequency pulse;
driving, by the laser driver, the laser diode with the current having a variable frequency pulse;
generating, by the laser diode, a variably pulsed laser beam;
transmitting the variably pulsed laser beam to the beam splitter;
splitting, by the beam splitter, the variably pulsed laser beam into a first portion which is reflected from the beam splitter and a second portion which passes through the beam splitter;
receiving, by the laser diode, the first portion;
receiving, by the eye of the photodetector, the second portion;
measuring, by the photodetector, an optical intensity of second portion;
generating, by the photodetector, an electrical signal based on the optical intensity;
amplifying, by a transimpedance amplifier, the electrical signal;
receiving, by a data acquisition (DAQ) system, the amplified electrical signal;
detecting, by the data acquisition (DAQ) system, a frequency f1 at which an average power of the variably pulsed laser beam peaks due to stimulated amplification, by the first portion reflected from the beamsplitter from the first location X1, of the variably pulsed laser beam generated by the laser diode;
moving the beamsplitter to a second location X2;
detecting, by the data acquisition (DAQ) system, a frequency f2 at which the average power of the variably pulsed laser beam peaks due to stimulated amplification, by the first portion reflected from the beamsplitter from the second location X2, of the variably pulsed laser beam generated by the laser diode;
and
calculating, by a computing device connected to the DAQ system, the speed of light v based on:
v
=
2
⁢
(
X
2
-
X
1
)
/
(
1
/
f
2
-
1
/
f
1
)
.

41 more elements

A system for determining the speed of light, comprising:

a linear stage;
a laser diode mounted at a distance X0 from the linear stage, wherein the laser diode is configured to generate a variably pulsed laser beam;
a beamsplitter mounted at a first location X1 on the linear stage, wherein the beamsplitter is configured to receive the variably pulsed laser beam from the laser diode;
a photodetector mounted at a distance Xp from the beamsplitter, wherein an eye of the photodetector is configured to receive a portion of the variably pulsed laser beam from the beamsplitter;
a laser driver operatively connected to the laser diode, wherein the laser driver is configured to generate a current having a variable frequency pulse, wherein the laser diode is configured to receive the current having a variable frequency pulse, generate a variably pulsed laser beam and transmit the variably pulsed laser beam to the beam splitter,
wherein the beamsplitter is configured to split the variably pulsed laser beam into a first portion which is reflected from the beam splitter back to the laser diode and a second portion which passes through the beam splitter and is transmitted to the photodetector,
wherein the eye of the photodetector is configured to receive the second portion transmitted from the beamsplitter from the first location X1,
wherein the photodetector is configured to measure an optical intensity of the second portion transmitted by the beamsplitter from the first location X1 and generate a first electrical signal based on the optical intensity;
a transimpedance amplifier connected to the photodetector, wherein the transimpedance amplifier is configured to amplify the first electrical signal;
a data acquisition (DAQ) system configured to receive the first amplified electrical signal and detect a frequency f1 at which an average power of the variably pulsed laser beam peaks due to stimulated amplification, by the first portion reflected from the beamsplitter from the first location X1, of the variably pulsed laser beam generated by the laser diode;
and
a computing device operatively connected to the DAQ system, wherein the computing device is configured to store the first location X1 and the frequency f1,
wherein the beamsplitter is configured to be moved to a second location X2,
wherein the beamsplitter at the second location X2 is configured to split the variably pulsed laser beam into a first portion which is reflected from the beam splitter back to the laser diode and a second portion which passes through the beam splitter and is transmitted to the photodetector,
wherein the eye of the photodetector is configured to receive the second portion transmitted by the beamsplitter from the second location X2,
wherein the photodetector is configured to measure an optical intensity of the second portion transmitted by the beamsplitter from the second location X2 and generate a second electrical signal based on the optical intensity,
wherein the transimpedance amplifier is configured to amplify the second electrical signal,
wherein the data acquisition (DAQ) system is further configured to receive the amplified second electrical signal and detect a frequency f2 at which an average power of the variably pulsed laser beam peaks due to stimulated amplification, by the first portion reflected from the beamsplitter from the second location X2, of the variably pulsed laser beam generated by the laser diode,
wherein the computer system is configured to store the second location X2 and the frequency f2,
wherein the computer system is further configured to calculate the speed of light v based on:
v
=
2
⁢
(
X
2
-
X
1
)
/
(
1
/
f
2
-
1
/
f
1
)
.

41 more elements

A system for determining the speed of light, comprising:

a linear stage;
a laser diode mounted at a distance X0 from the linear stage;
a laser driver operatively connected to the laser diode, wherein the laser driver is configured to generate a current having a variable frequency pulse, wherein the laser diode is configured to receive the current having a variable frequency pulse, generate a variably pulsed laser beam and transmit the variably pulsed laser beam;
a mirror mounted at a first location X1 on the linear stage, wherein the mirror is configured to receive the variably pulsed laser beam from the laser diode and reflect a portion of the variably pulsed laser beam back to the laser diode as feedback, wherein the feedback generates stimulated amplification of the variably pulsed laser beam;
a photodetector configured to receive the amplified variably pulsed laser beam from the laser diode;
wherein the photodetector is configured to measure an optical intensity of the second portion transmitted by the mirror from the first location X1 and generate a first electrical signal based on the optical intensity;
a transimpedance amplifier connected to the photodetector, wherein the transimpedance amplifier is configured to amplify the first electrical signal;
a data acquisition (DAQ) system configured to receive the first amplified electrical signal and detect a frequency f1 at which an average power of the variably pulsed laser beam peaks due to stimulated amplification, by the first portion reflected from the mirror from the first location X1, of the variably pulsed laser beam generated by the laser diode;
and
a computer system operatively connected to the DAQ system, wherein the computer system is configured to store the first location X1 and the frequency f1, wherein the mirror is configured to be moved to a second location X2 on the linear stage;
wherein the eye of the photodetector is configured to receive the second portion transmitted by the mirror from the second location X2,
wherein the photodetector is configured to measure an optical intensity of the second portion transmitted by the mirror from the second location X2 and generate a second electrical signal based on the optical intensity,
wherein the transimpedance amplifier is configured to amplify the second electrical signal,
wherein the data acquisition (DAQ) system is further configured to receive the amplified second electrical signal and detect a frequency f2 at which an average power of the variably pulsed laser beam peaks due to stimulated amplification, by the first portion reflected from the mirror from the second location X2, of the variably pulsed laser beam generated by the laser diode,
wherein the computer system is configured to store the second location X2 and the frequency f2,
wherein the computer system is further configured to calculate the speed of light v based on:
v
=
2
⁢
(
X
2
-
X
1
)
/
(
1
/
f
2
-
1
/
f
1
)
.

37 more elements

Dependencies are inferred from the claim text.

Facts

Application: 18/952,818Filed 19 Nov 2024
Priority: 20 Nov 2023
Published: 22 May 2025
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

G01J 1/42
Photometry, e.g. photographic exposure meter: using electric radiation detectors
G01S 11/12
Systems for determining distance or velocity not using reflection or reradiation: using electromagnetic waves other than radio waves
G01J 1/0407
Optical or mechanical part supplementary adjustable parts: optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings
G01J 1/4257
Using electric radiation detectors: applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam