Senior Fitness - Exercise and Nutrition for Aging Men and Women
FREE Article Feed for your website.
Home Ownership Magazine
Party Planning Information
Article Marketing Resources
Bio-Medical Research Article Database
Informative Articles on Life, Love and Happiness
Tutorials on Business to Writing
Famous Quotes from Famous People
Song Lyric Information
New US Patent Information
Comprehensive List of Content by Category
Online Auctions and Shopping Related Articles
Article Search
Most Recent Articles
 

Credit Card Facts
Category:
Finance / Investment  

Got Bills to Pay You ve got a Decision to Make
Category:
Business  

What to look for when getting a loan
Category:
Business  

Are UK Secured Loans a part of your financial portfolio
Category:
Business  

How things change
Category:
Marketing  

Eating Well While Traveling
Category:
Travel  

The never ending Spyware story
Category:
Computers  

Raise Your Income
Category:
Marketing  

Is There A Single Acne Cure That Will Work For Everyone
Category:
Health / Fitness  

Hypertension Determining If You Are At Risk
Category:
Health / Fitness  

Making Money With Niche Products
Category:
Marketing  

Euro Pound brief property Almeria Spain 2nd August 2006
Category:
Business  

The Best Way To Generate Free Targeted Website Traffic
Category:
Marketing  

Credit Cards Answers to the Approval Process
Category:
Finance / Investment  

Croydon Hotels Hotels in Croydon Cheap B and B Accommodation nea...
Category:
Travel  

Is Growing Saint George Utah The New Palm Springs
Category:
Travel  

Contact Lenses Have Come A Long Way To Give You Simple Hassle Fr...
Category:
Health / Fitness  

Why Secondary research is preferred for Market research Report
Category:
Business  

Traffic Generation Using Only Free Methods
Category:
Business  

Golf Fitness Tips Five Benefits Of Adding A Few Simple Exercises...
Category:
Sports  

Discover The Simple Method Of Fat Loss No One Else Will Tell You...
Category:
Health / Fitness  

Failure is Part of Success
Category:
Business  

Two Things You Do Not Know About LASIK Eye Surgery
Category:
Health / Fitness  

Tennis A sport your love handles hate
Category:
Sports  

Vitamins for Depression
Category:
Health / Fitness  

The Best Countertops Are Granite
Category:
Home And Family  

Life Insurance Should be Death Insurance but they d have a hard ...
Category:
Business  

The Fastest Way To Secure A Loan
Category:
Marketing  

What is better for carpet cleaning Steam cleaners or regular vac...
Category:
Home And Family  

Free Ebook Demonstrates Your Path To The Top Of The Search Engin...
Category:
Business  

Homoeopathy
Category:
Health / Fitness  

Cosmetic Surgery for Those in their 40s and Up
Category:
Health / Fitness  

Flax Seed a source for omega 3 fatty acids
Category:
Health / Fitness  

How do negative affirmations affect my life
Category:
Marketing  

Cheap Airfares Ways To Secure It
Category:
Finance / Investment  

When the Cardiologist says you have heart disease part 2
Category:
Health / Fitness  

Virtual Economy in MMORPGs
Category:
Business  

Bedding Basics What s Inside Your Bed
Category:
Home And Family  

Top Ten Secrets to Saving Big Money in the Airline Flights
Category:
Finance / Investment  

CRM 101 The Basics of Customer Relationship Management
Category:
Business  

Baby Shower Fun Activities
Category:
Home And Family  

Beach front Vacation Homes
Category:
Travel  

Protecting Yourself During Your European Jaunt
Category:
Finance / Investment  

Finding Sales Leads For Your Cleaning Business
Category:
Business  

FIFA
Category:
Sports  

When Early Signs of Menopause Strike Women
Category:
Health / Fitness  

Stop Losing Money and Get into an Investment Opportunity
Category:
Business  

Some tips about analysis of the advance of the site
Category:
Marketing  

ACRX Donates Free Rx Cards To YWCA Of Greater Toledo
Category:
Business  

Tips On How To Choose Winning Stock
Category:
Business  

Collection Of Classical Music Cd
Category:
Entertainment / Television  

Dry chemical carpet cleaning for your carpet
Category:
Home And Family  

Parents You can become financially successful
Category:
Finance / Investment  

How to remove stains from your carpet
Category:
Home And Family  

Getting the Best Natural Skin Care for Your Money
Category:
Health / Fitness  

What not to do when negotiating your Surrey lease
Category:
Business  

Easy Way to Increase Your Online Income
Category:
Business  

On Page SEO in five easy steps
Category:
Marketing  

Creating a Business Plan
Category:
Business  

What are MLM Leads
Category:
Business  

Happy Relationships
Category:
Home And Family  

Take Control Of Your Home Heating Oil Costs This Winter
Category:
Home And Family  

Your Own Com
Category:
Business  

Support is key to success for any company
Category:
Business  

An Overview of Unsecured Loans
Category:
Business  

Is Internet Marketing Dead
Category:
Marketing  

Night of the Living Debt How Re Aged Bills Can Hurt You
Category:
Finance / Investment  

Design is Key to Trade Show Exhibit Success
Category:
Marketing  

Best Practices For Website Directory Submissions
Category:
Marketing  

4 Questions You Need to Answer Before You Tear Down the Walls
Category:
Home And Family  

Choosing the Right Ladder for Your Home
Category:
Home And Family  

Do Blood Types Really Matter
Category:
Entertainment / Television  

Ideal Web Hosting WebHostingInsider
Category:
Computers  

Spiti The Hidden Valley Part I
Category:
Travel  

Dynamic Product Search
Category:
Business

Broad-band variable-wavelength laser beam generator Number:7,154,920 from the United States Patent and Trademark Office (PTO) owispatent

Home    Author Login    Submit Article    Article Search    Add Your Link    Edit Your Link    Contact Us    Advertising    Disclaimer

   

 
Web LinkGrinder.com

Top Breaking News
     Greek, Cypriot Leaders Resume Unification Talks in Nicosia by Nathan Morley
     Indonesia Tobacco Sales Grow, Raising Health Fears
     South Korea Allows Top Defector to Travel Overseas by VOA News

Title: Broad-band variable-wavelength laser beam generator

Abstract: There is provided a broadly tunable laser beam generator serving as a laser beam source which utilizes a nonlinear optical effect of a silica (glass) fiber and which is broadly tunable in the near-infrared region, having ultra-broad tunability which has not been easily achieved by known tunable lasers, and generating coherent light which can be continuously swept over the entire wavelength region with a simple mechanical operation of a single wavelength selecting element and which is emitted in a constant direction independent of its wavelength.The laser beam source which utilizes a nonlinear optical effect of a silica optical fiber (8) and which is broadly tunable in the near-infrared region has ultra-broad tunability and generates coherent light which can be continuously swept over the entire wavelength region with a single wavelength selecting element (10).

Patent Number: 7,154,920 Issued on 12/26/2006 to Fukatsu


Inventors: Fukatsu; Susumu (Tokyo, JP)
Assignee: Japan Science and Technology Agency (Kawaguchi, JP)
Appl. No.: 10/484,811
Filed: July 31, 2002
PCT Filed: July 31, 2002
PCT No.: PCT/JP02/07782
371(c)(1),(2),(4) Date: January 30, 2004
PCT Pub. No.: WO03/012544
PCT Pub. Date: February 13, 2003


Foreign Application Priority Data

Jul 31, 2001 [JP] 2001-231555

Current U.S. Class: 372/20 ; 359/341.1; 372/29.02
Current International Class: H01S 3/10 (20060101); H01S 3/00 (20060101)
Field of Search: 372/21,29.02,29.022 359/341.1-341


References Cited [Referenced By]

U.S. Patent Documents
4784450 November 1988 Jain et al.
5862162 January 1999 Maeda
5923683 July 1999 Morioka et al.
6396574 May 2002 Lee et al.
6407869 June 2002 Asami
6625182 September 2003 Kuksenkov et al.
Foreign Patent Documents
03293788 Dec., 1991 JP

Other References

Ilev. I. et al., Highly efficient wideband continuum generation in a single-mode optical fiber by powerful broadband laser pumping. Applied Optics, May 20, 1996, vol. 35, No. 15, pp. 2548 to 2553. cited by other .
Grigoryants, V.V. et al., Nonlinear conversion of laser radiation in optical fibers and its applications for spectral invertigation. Optical and Quantum Electronics, 1983, vol. 15, No. 4, pp. 363 to 365. cited by other.

Primary Examiner: Menefee; James
Assistant Examiner: Nguyen; Phillip
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.

Claims



The invention claimed is:

1. A broadly tunable laser beam generator comprising: a pump pulse laser; an output-coupling half-mirror configured to pass a pulse beam emitted from the pump pulse laser therethrough; a silica optical fiber configured to receive the pulse beam from the output-coupling half-mirror via a first collective collimator lens, the silica optical fiber having a birefringence and a cut-off wavelength from 1100 to 1300 nm; and a single-wavelength selecting element configured to receive the beam emitted from the silica optical fiber via a second collective collimator lens and feeding back a light with a specific wavelength, wherein the feedback light with the specific wavelength is received by the silica optical fiber via the second collective collimator lens, amplified to obtain a gain while propagating through the fiber twice, emitted from the fiber, converted into collimated light by the first collective collimator lens, and emitted from the output-coupling half-mirror as an output light beam.

2. The broadly tunable laser beam generator according to claim 1, wherein the tunability is completely continuous to a degenerate region close to the pump light.

3. The broadly tunable laser beam generator according to claim 1, wherein by coupling a pulse laser beam source with an end face of the fiber so as to input a pulse laser beam having a short wavelength close to the cut-off wavelength into the end face of the fiber as pump light, stimulated Raman scattering and stimulated parametric four-lightwave mixing occur in the silica fiber so as to provide a gain spectrum continuously extending over both shorter and longer wavelength regions with respect to a wavelength of the pump light, and consequently to provide ultra-broadband tunability, the ultra-broad tunability lying from 800 nm to 1875 nm.
Description



TECHNICAL FIELD

The present invention relates to a broadly tunable laser beam generator.

BACKGROUND ART

In the fields of optics in general including spectroscopy and optical communications, a light source offering a broadband tunability has been eagerly desired. Although the term "broadband" is generic and defined only vaguely, it here points to a band from 800 to 1800 nm that is of importance in the fields of spectroscopy and optical communications. In many applications, an incandescent lamp or the like combined with a spectrometer has been the optimal choice as a broadly tunable light source; the intensity of light remains no more than a few tens of .mu.W per 1 nm, and even worse, convergence of light is not as good as that of coherent light like laser radiation. This is solely attributable to incoherence of light generated in an incandescent lamp.

Driven by the same desire, several lasers as a coherent light source having a fair tunability have been developed. In fact, some of them have been put in practical use in the many and expanding fields of application.

DISCLOSURE OF INVENTION

Among those tunable lasers developed so far, a Ti-sapphire laser is a well-known example, which is capable of tuning 300 nm continuously. The widest tuning range is provided by an optical parametric oscillator (OPO) laser, which can go from the ultraviolet all the way to the infrared with the aid of the third-order nonlinearity in an optical crystal of macroscopic size. However, there are still problems associated with the OPO: wavelength sweep is not easy in the pump-light degenerate region, an oscillation linewidth is broad (>1 nm), an light-emitting direction varies with wavelength unless appropriate angle compensation is exercised, and very high-power pump light is required.

Meanwhile, fiber lasers utilizing an optical fiber as a broadband gain medium have been already on the market, such as a tunable Raman laser. For these commercial fiber lasers, a broad wavelength tuning range 1073 to 1600 nm is predicted according to literature values of tunability due to the third-order nonlinearity. However, the tuning range is deliberately limited to within 100 nm in practice as there is a trade-off between the broad tunability and small spectral linewidth. It is sometimes even required to designate a particular wavelength and thus the potential broad tunability is not taken advantage of.

In addition, it has been taken for granted that as long as stimulated Raman scattering is concerned, low-energy light (Stokes light or down-converted light) is what is mainly generated, and up-converted light (anti-Stoke light) is very unlikely and thus wavelength tuning is not allowed in the pump-light degenerate region as well as at the high energy side.

In view of the above-mentioned circumstances, it is an objective of the present invention to provide a broadly tunable laser beam generator serving as a laser beam source which utilizes a nonlinear optical effect of a silica (glass) optical fiber and which is broadly tunable in the near-infrared region, offering ultra-broadband tunability that has not been easily achieved by the known tunable lasers, and generating coherent light whose direction of emission does not depend on wavelength and which scans the entire wavelength region with a single wavelength selecting element.

In order to achieve the above objective, according to the present invention, [1] a silica optical fiber having birefringence is used as a gain medium, and a non-linear optical effect of the fiber (stimulated Raman scattering and stimulated parametric four-lightwave mixing) is utilized; [2] by using a pulse laser having an oscillating wavelength shorter than a cut-off wavelength as pump light, a gain spectrum continuously extending in the degenerate region in the vicinity of the pump light and also over both a shorter wavelength (anti-Stokes light) region and a longer wavelength (Stokes light) region with respect to a wavelength of the pump light is generated; [3] a diffraction grating is used as a broadly tunable single wavelength selecting element; [4] a collinear emitting configuration for generating a laser beam from an end of the fiber is employed; and [5] a laser gain is obtained by passing light through the fiber twice without requiring pulse-tuning adjustment.

A tunable range of 800 to 1800 nm according to the present invention covers even 210 THz on an energy scale. Such a light source (laser) easily tunable across a broadband with direction of emission remaining collinear and configured in a simple geometry is unparalleled.

Here the term "collinear" means that light in the laser oscillator has a particular direction of emission regardless of wavelengths: light always emits from the end of the fiber so that it is oriented towards a fixed direction in space. This is well contrasted with the case of OPO. Since direction of emission of a laser beam generated in an OPO crystal often varies with wavelength as it is scanned, it is required to introduce a second crystal to compensate for the angular departure. This results in a complicated structure and operation. Even worse, the OPO still cannot get rid of the problem that the laser beam is not perfectly collinear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a broadly tunable laser beam generator according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating tuning characteristics according to the embodiment of the present invention.

FIG. 3 is a diagram of single wavelength selection according to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described in detail.

FIG. 1 is a diagrammatic view of a broadly tunable laser beam generator according to the embodiment of the present invention, FIG. 2 is a diagram illustrating tuning characteristics according to the embodiment of the present invention, wherein the horizontal and vertical axes respectively indicate an oscillating wavelength (in nm) and a relative optical-output intensity (in dB). FIG. 3 demonstrates specific examples of single-wavelength selection, wherein the horizontal and vertical axes respectively indicate a wavelength (in nm) and a relative optical-output intensity (on an arbitrary scale), and the three examples of wavelength selection shown have been shifted along the vertical axis for clarity. The peak at the extreme left indicates a pump laser beam as a reference.

In FIG. 1, the reference numeral 1 denotes a pump pulse laser, 2 denotes directions of polarized light of the pumping pulse laser 1, 3 denotes a polarization beam splitter, 4 denotes a quarter-wave plate, 5 denotes a direction of circularly polarized light generated by the quarter-wave plate 4, 6 denotes an output-coupling half-mirror, 7 and 9 denote collective collimator lenses, 8 denotes a silica optical fiber serving as a gain medium, and 10 denotes a diffraction grating serving as a single-wavelength selecting element.

Although the polarization beam splitter 3 and the quarter-wave plate 4 constitute an isolator to remove unwanted pump reflection that is fedback to the pump laser 1, they may be replaced with an alternate photonic device having the same function as them. In addition, even when the polarization beam splitter 3 and the quarter-wave plate 4 are removed, the generation characteristics of a broadband tunable laser beam according to the present invention is not affected.

A pulse beam emitted from the pump pulse laser 1 (with an oscillating wavelength of 1064 nm) (it may be a Q-switched or mode-locked pulse laser which can generate a high-power pulse beam, and more preferably, it may be the one with a pulse beam having an output intensity of 1 kW or more and having oscillating wavelengths shorter than a cut-off wavelength of the single-mode silica optical fiber 8 by about 10 to 20% in addition to 1064 nm) passes through the output-coupling half-mirror 6 and is incident on the silica optical fiber 8 serving as a gain medium via the collective collimator lens 7.

The silica optical fiber 8 is a single mode fiber having a birefringent characteristic, a cut-off wavelength of 1100 nm to 1300 nm, and a length of 100 m to 400 m. When a polarization-preserving fiber is used, the fiber length can be made even shorter. Also, in order to achieve this purpose, even a refractive-index-gradient-type multimode fiber (graded-index fiber) for communications, having 50 and 62.5 .mu.m core diameters, can be used instead of a single mode fiber, aside from the fact that its output-light intensity characteristics is different from those of the single mode fiber.

While pulse light is propagating through the silica optical fiber 8, a nonlinear optical effect of silica glass allows stimulated Raman scattering and stimulated parametric four-wave mixing. Phase-matching conditions of the former are automatically satisfied with dispersion of phonons, and those of the latter is compensated for with modal dispersion of wavelengths shorter than the cut-off wavelength, caused by a waveguide.

The light emitted from the other end of the silica optical fiber 8 is converted into collimated light by the collective collimator lens 9 and is incident on the diffraction grating 10, and only first-order diffracted light is selectively fed back to the silica optical fiber 8. Preferably, the diffraction grating (single-wavelength selecting element) 10 maintains a high reflectance in a working wavelength band in order to improve a feedback efficiency.

To be specific, with 830 to 1000 nm in blaze wavelength, 600 to 1200 lines/mm, 10.times.10 mm.sup.2 to 25.times.25 mm.sup.2, and gold or aluminum coating, the diffraction grating offers an excellent result. Alternatively, a combination of a narrow-linewidth band-pass filter and a total reflection mirror may be used.

The fed back light having a specific wavelength is amplified by obtaining a gain while propagating through the fiber twice in both directions, is emitted from the one end of the fiber on which it was first incident, is converted into collimated light by the collective collimator lens 7, and is emitted as an output light beam by the output-coupling half-mirror 6. It is emitted in a constant direction independent of its wavelength, that is, it becomes collinear.

Although the highest output is in principle obtained when the reflectance of the output-coupling half-mirror 6 is 50%, it may be 10 to 50%.

Measured results of light outputs in FIG. 2 are shown by relative intensities normalized by one of the measured results of 3 mW at 1178 nm. An absolute output of a laser according to the present invention can be increased substantially in proportion to a pump intensity. As is obvious from FIG. 2, ultra-broadband tunability lies from 800 nm to 1875 nm, and a Raman and four-wave mixing gear cannot be primarily expected out of this wavelength region.

As single-wavelength selection characteristics is shown in FIG. 3, with the above-described structure, a linewidth (full width at half maximum) of 1 nm or less is obtained, and the linewidth can be further narrower in reverse proportion to the grooved line density of the diffraction grating used for feedback of light.

Meanwhile, the present invention is not limited to the foregoing embodiment, and, since a variety of modifications are possible based on the spirit of the present inventions, these modifications shall not be excluded from the scope of the present invention.

As described above in detail, according to the present invention, a laser beam generator (coherent light source) which is tunable in a broadband can be constructed. A tunable region of 800 to 1875 nm is useful in a very wide range and immediately available as an excitation light source for spectroscopy including a solid state matter, and also covers all wavelength bands of 830 nm, 1310 nm, 1480 nm, and 1500 to 1600 nm which are important in optical communications. Especially, in the latter case, although an efficiency of coupling the light source to a fiber is vital, since a laser beam is emitted from the fiber itself, its coupling efficiency is about twice as much as that of spatial beam coupling, and also it is advantageous from the view point of maintenance because of no loss caused by scattering.

Also, the generator has a simpler structure than an optical parametric oscillator (OPO), collinearly emits light independent of its wavelength, and also easily performs wavelength selection.

INDUSTRIAL APPLICABILITY

A broadly tunable laser beam generator according to the present invention is suitable as a coherent, broadband tunable light source of a fiber-emitting-type in the field of spectroscopy and as a coherent tunable light source having a fiber-pigtail specification in the field of optical communications.

*


Free Web Sudoku Puzzles.
Solve with your browser.
    2         5  
3 7     5       1
      9 8        
            8 1  
    5 1 3 7 4    
  6 7            
        4 2      
9       6     2 3
  8         1    
What is it?



Add Your Site · Terms Of Service · Privacy Policy


DISCLAIMER
Linkgrinder is a free service that searches the Internet and indexes all files found so that you may search quickly and easily for shared files. These files are created and made available individually by users whose identity we are not aware of and who we have no control over. In essence we function like a search engine tool; these files ARE NOT STORED OR SERVED BY OUR NETWORK. We are not responsible for any materials obtained by using our service. We do not monitor any of the contents of these files. These files may contain viruses, illegal materials, materials inappropriate for minors, offensive files and the like. BY USING OUR SERVICE, YOU ASSUME FULL RESPONSIBILITY FOR DOWNLOADING THESE MATERIALS AND WILL INDEMNIFY US FOR ANY DAMAGES THAT MAY BE INCURRED.

For More Specific Information VIEW OUR TERMS OF SERVICE.

Thank you and Enjoy!