Tunable Laser (1).pptx

Tunable Laser,Basic tunable Laser Setup, Tunable Laser diode, Tunable Laser Optics, History, Tunable laser Absorption Spectrometer, Types and categories of Tunable Lasers, solid-state bulk laser, Dye lasers, Types of tenability, Single line tuning, Multi-line tuning, Narrowband tuning, Simulating Laser Tuning, Wavelength-swept Lasers, Dynamic sensors based on wavelength-swept lasers, Wavelength-swept Lasers Spectrum, Widely tunable lasers,Quantum cascade lasers, Applications of Tunable Lasers, Suppliers,Laser Quantum, NKT Photonics, TOPTICA photonics

1. Hajira Mahmood Ph .D Analytical Chemistry Scholar

2. Contents Definitions History Basic Principal Types Applications References

3. Tunable Laser Definition: “A laser that can change its frequency over a given range .” A   tunable laser  is a  laser  whose wavelength of action can be altered in a skillful mode. Tunable laser can also be defined as: “Any form of laser ; e.g., a dye laser, having an output that can be adjusted over a wide range of wavelengths, typically 70 nm wide.”

4. Basic tunable Laser Setup

5. Tunable Laser diode

6. Tunable Laser Optics Broadly tunable lasers continue to have an enormous impact in many diverse fields of science and technology. From a renaissance in spectroscopy to laser guide stars and laser cooling, the nexus is the tunable laser. It offers a transparent and comprehensive treatment of the physics

7. History The first true broadly tunable laser was the dye laser  in 1966 .   The first narrow-line width tunable laser is introduced in 1972, allowing tuning over a range of tens to hundreds of nanometers.   T he most common tunable solid-state laser is Titanium-doped sapphire laser, capable of laser operation from 670 nm to 1,100 nm wavelength. Typically these laser systems incorporate a  Lyot filter  into the laser cavity, which is rotated to tune the laser. Other tuning techniques involve diffraction gratings, prisms, etalons, and combinations of these .   Multiple principal arrangements in several configurations as described by  Duarte are used in diode, dye, gas, and other tunable lasers .

8. Tunable laser Absorption S pectrometer

9. Types and categories of Tunable Lasers   Following are the types of tunable laser among those of solid, liquid and of gas state. Carbon dioxide laser Dye laser (Liquid and solid state laser) Crystal and diode laser (Semiconductor) Free electron laser

10. solid-state   bulk laser A few  solid-state   bulk laser in particular  titanium–sapphire lasers  and  Cr:ZnSe and Cr:ZnS  lasers allow tuning over hundreds of nanometers in the near- and mid- infrared spectral region. In general,  transition-metal doped gain media  offer larger tuning ranges than  rare-earth-doped gain media , since the electrons involved in such media interact more strongly with the host lattice; see the article on  vibrosnic lasers . Output powers can be hundreds or even thousands of milliwatts .

11. Dye lasers   Dye lasers  also allow for broadband tunability . Different dyes can cover very broad wavelength ranges, e.g. throughout the visible region. There are  narrow- linewidth dye laser systems  ( continuous-wave  or  pulsed ) for use in  laser spectroscopy , and also  mode-locked  dye lasers generating  femtosecond pulses . Some  free electron lasers  can cover enormously broad wavelength ranges, and often in extreme spectral regions.

12. Types of tenability Single line tuning: A ll lasers can emit light in line width  of the laser transition having a narrowing 1,064  nm wavelength. For example:   Nd : YAG laser has a line width of approximately 120 GHz, or 0.45  nm . Tuning of the laser output across this range can be achieved by placing wavelength-selective optical elements i.e   etalon into the laser's optical cavity to provide selection of a particular longitudinal mode of the cavity.

13. Multi-line tuning Most laser gain media have a number of transition wavelengths on which laser operation can be achieved. For example, as well as the principal 1,064 nm output line, Nd:YAG has weaker transitions at wavelengths of 1,052 nm, 1,074 nm, 1,112 nm, 1,319 nm, and a number of other lines .  Usually, these lines do not operate unless the gain of the strongest transition is suppressed; e.g., by use of wavelength-selective dielectric laser. If a dispersive   element prism introduced into the optical cavity, tilting of the cavity's mirrors can cause tuning of the laser as it "hops" between different laser lines. Such schemes are common in  argon - ion lasers allowing tuning of the laser to a number of lines from the  ultraviolet  and  blue  through to  green  wavelengths .

14. For some lasers the laser's cavity length can be modified and can be continuously tuned over a significant wavelength range . Distributed feedback (DFB ) semiconductor lasers and vertical cavity surface emitting lasers (VCSELs) use periodic distributed Bragg reflector (DBR) structures to form the mirrors of the optical cavity . If the  temperature of the laser is changed, the index change of the DBR structure causes a shift in its peak reflective wavelength and the wavelength of the laser . Narrowband tuning

15. Simulating Laser Tuning With the software  RP Fiber Power  one can simulate the tuning behavior of broadband laser, taking into account ASE, limitations of bandpass filters, etc. Use that to find out the requirements on the laser tuner . Figure 1:  Setup of a tunable solid-state bulk laser, realized e.g. with a Ti:sapphire laser crystal

16. Wavelength-swept Lasers There are certain Juniper lasers which are optimized such that the output wavelength can be periodically and rapidly swept through a substantial range.

17. Dynamic sensors based on wavelength-swept lasers

18. Wavelength-swept Lasers Spectrum

19. Widely tunable lasers A typical laser diode. When mounted with external optics these lasers can be tuned mainly in the red and near infrared. Sample Grating Distributed Bragg Reflector lasers (SG-DBR) have a much larger tunable range, by the use of vernier tunable  Bragg mirrors  and a phase section, a single mode output range of >50 nm can be selected. Other technologies to achieve wide tuning ranges for  DWDM -systems  are:

20. External cavity lasers using a MEMS structure for tuning the cavity length, such as devices commercialized by  Iolon . External cavity lasers using multiple-prism grating arrangements for wide-range tunability . DFB laser arrays based on several thermal tuned DFB lasers: Coarse tuning is achieved by selecting the correct laser bar. Fine tuning is then done thermally, such as devices commercialized by  Santur Corporation. Tunable VCSEL: One of the two mirror stacks is movable. To achieve sufficient output power out of a VCSEL structure, lasers in the 1,550 nm domain are usually either optically pumped or have an additional optical amplifier built into the device. As of December 2008 there is no widely tunable VCSEL commercially available any more for DWDM-system application . It is claimed that the first infrared laser with a tunability of more than one octave was a germanium crystal laser .

21. The   prism pair  spatially disperses the different wavelength components, so that the movable slit can be used to shift the wavelength away from that of maximum gain. Other types of lasers offer tuning ranges spanning a few nanometers to some tens of nanometers: Rare-earth-doped   fiber lasers , e.g. based on  ytterbium , can often be tuned over tens of nanometers, sometimes even more than 100 nm. Most  Raman fiber lasers  also have the potential for wideband tuning. Some  rare-earth-doped   laser crystals , often doped with  ytterbium , also allow for substantial tuning ranges of  bulk lasers . Examples are  tungstates ,  vanadates , Yb:BOYS , and Yb:CALGO . Color center lasers  rely on broadband gain from certain lattice defects in a crystal, which can be generated e.g. with gamma irradiation. They are not widely used, however. Most  laser diodes  can be tuned over a few nanometers (often by varying the junction temperature), but some special types such as  external-cavity diode lasers  and  distributed Bragg reflector lasers  can be tuned over 40 nm and more.

22. Quantum cascade lasers Quantum cascade lasers  are also broadly tunable mid- infrared  laser sources. Some fine tuning, often continuously without mode hops, is possible for other lasers: Some  compact  solid-state   bulk lasers  such as  nonplanar ring oscillators  (NPROs, MISERs) allow continuous tuning within their  free spectral range  of several gigahertz. Tuning may be accomplished by applying stress to the  laser crystal  via a piezo, or by varying the crystal temperature. Similar fine tuning is possible with some  single-frequency   laser diodes , e.g. by varying the drive current. For wideband tuning in various spectral regions,  optical parametric oscillators  (OPOs) can be used. These are actually not  lasers , but OPO sources are nevertheless sometimes included with the term  tunable laser sources .

23. Applications of Tunable Lasers Wavelength-tunable laser sources have many applications, some examples of which are: In laser absorption spectroscopy, a wavelength-tunable laser with narrow optical bandwidth  used for recording absorption spectra with very high frequency resolution. In a LIDAR system, it may be tuned to a wavelength which is specific to a certain substance to be monitored. Tuning to atomic resonances is also used in laser isotope separation. The laser is then tuned to a particular isotope in order to ionize these atoms and subsequently deflect them with an electric field. A tunable laser can be used for device characterization, e.g. of photonic integrated circuits.

24. In optical fiber communications with wavelength division multiplexing, a tunable laser can serve as a spare in the case that one of the fixed-wavelength lasers for the particular channels fails. Even though the cost for a tunable laser is higher, its use can be economical as a single spare laser can work on any transmission channel where it is needed. As the cost of tunable lasers is no longer much higher than for non-tunable ones, tunable lasers are now often even used throughout. In optical frequency metrology, it is often necessary to stabilize the wavelength of a laser to a certain reference standard (e.g. a  multipass gas cell or an optical reference cavity). This can be accomplished e.g. with an electronic feedback system, which automatically adjusts the laser wavelength. Some interferometers and fiber-optic sensors profit from a wavelength-tunable laser source, e.g. if this makes it possible to remove an ambiguity or to avoid mechanical scanning of an optical path length.

25. Suppliers The   RP Photonics Buyer's Guide  contains 84 suppliers for tunable lasers. Among them : RPMC Lasers RPMC Lasers offers a  tunable DPSS laser  that uses an Optical Parametric Oscillator (OPO) to produce tunable wavelengths in 410 – 2300 nm range. Its advanced laser design results in a compact, user-friendly turnkey system that requires little maintenance. It integrates all laser electronics into the housing and there are no chillers or bulky power supplies needed.

26. APE The tunable picosecond laser source  pico Emerald  emits ultrashort pulses with a duration of 2 picoseconds (other durations possible). A wavelength scan / sweep function for fast spectra acquisition over certain specific wavelengths is included.

27. EKSPLA Tunable lasers  with ultra-wide tuning range – from 210 nm to 12000  nm.

28. Laser Quantum Many of Laser Quantum’s  ultrafast lasers  can be tuned to different wavelengths for various scientific applications, ranging from 720 nm – 930 nm to meet the specific needs of the application. Products include the  taccor tune  with touch-screen beam control, and the  helixx  with a unique 250 MHz repetition rate .

29. NKT Photonics The   SuperK EXTREME supercontinuum white light lasers  are broadband like a lamp and bright as a laser. They deliver high brightness diffraction limited light in the entire 400–2400 nm region and by adding one of our computer-controlled filters,  the SuperK VARIA , the SuperK can be converted into an ultra-tunable laser with up to 16 simultaneous lines, providing a continuous tunable output from 400 to 840 nm. Our  SuperK lasers   lasers are maintenance free and the fully fiber monolithic architecture ensures excellent reliability and a lifetime of thousands of hours.

30. TOPTICA photonics TOPTICA offers various  tunable diode laser systems . The combined spectral coverage is from 190 nm to 3500 nm, powers up to 4 W ( TA ), mode-hop-free tuning up to 110 nm ( CTL ).

31. Applications E xtremely widely in spectral resolution When coupled to the right filter In basic   absorptionand   photoluminescence study. F or solar cells characterization in a light beam induced current (LBIC) experiment F or the characterization of gold  nanoparticles  and single-walled carbon nanotube thermopile. Tunable sources were recently used for the development of  hyper spectral imaging As a powerful tool for reflection and transmission  spectroscopy, photobiology detector calibration, hyper spectral imaging and steady-state pump probe experiment.

32. Broadly tunable lasers continue to have a tremendous impact in many and diverse fields of science and technology. From a renaissance in laser spectroscopy to Bose-Einstein condensation, the one nexus is the tunable laser. Tunable Laser Applications describes the physics and architectures of widely applied tunable laser sources. Fully updated and ex Dense wavelength division multiplexing networks: principles and applications (published paper) Abstract: The very broad bandwidth of low-loss optical transmission in a single-mode fiber and the recent improvements in single-frequency tunable lasers have stimulated significant advances in dense wavelength division multiplexed optical networks. This technology, including wavelength-sensitive optical switching and routing elements and passive optical elements, has made it possible to consider the use of wavelength as another dimension, in addition to time and space, in network and switch design. The independence of optical signals at different wavelengths makes this a natural choice for multiple-access networks, for applications which benefit from shared transmission media, and for networks in which very large throughputs are required. Recent progress in multiwavelength networks are reviewed, some of the limitations which affect the performance of such networks are discussed, and examples of several network and switch proposals based on these ideas are presented. Discussed also are critical technologies that are essential to progress in this field .

33. Tunable Lasers for DIAL Applications (published paper ) The development of the DIAL technique has been limited by the availability of suitable tunablelaser sources. This review describes the four types of tunable laser that are most widelyused in DIAL applications. These are dye lasers, tunable solid state lasers, line tunable carbondioxide lasers and optical parametric oscillators .

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