Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
  • H01S3/0064—Anti-reflection devices, e.g. optical isolaters
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
  • H01S3/0092—Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/09—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on magneto-optical elements, e.g. exhibiting Faraday effect
  • G02F1/093—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on magneto-optical elements, e.g. exhibiting Faraday effect used as non-reciprocal devices, e.g. optical isolators, circulators
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
  • H01S3/0078—Frequency filtering
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
  • H01S3/06—Construction or shape of active medium
  • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
  • H01S3/067—Fibre lasers
  • H01S3/06754—Fibre amplifiers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
  • H01S3/16—Solid materials
  • H01S3/1601—Solid materials characterised by an active (lasing) ion
  • H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
  • H01S3/1618—Solid materials characterised by an active (lasing) ion rare earth ytterbium
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/30—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects
  • H01S3/302—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects in an optical fibre

Definitions

• the present invention relates to an optical isolation method for performing optical isolation by spectral filter and gain band.
• Fibre lasers attract considerable attention due to their extraordinary advantages such as high beam quality, high conversion efficiency and the ability of generating high average powers.
• ultra high-speed fibre lasers draw great interest owing to their applications in industry, medicine and scientific researches.
• Application of picosecond and femtosecond pulses in precision micromachining and surface changes has increased significantly in recent years.
• Highly-sensitive interaction of ultra high-speed lasers that generate picosecond or femtosecond pulses, with materials causes such lasers to penetrate into industrial material processing more and to increase.
• laser light reflects back from working surfaces during laser processing and it has an adverse effect on the laser performance. Due to the fact that back reflection results from the plasma shield created by laser beams during its interaction with the target material, this plasma shield guides the back-reflected light excellently and it ensures that the laser beam is guided to the laser wherefrom it originates, even if it is meters away. While the final and the most powerful amplifying stage of the laser is exposed to the greatest danger, back reflection can be amplified within the laser system and the master oscillator may damage previous amplification stages and even the source laser in laser systems based on power amplifier. It is standard practice to use an optical isolator so as to protect a laser from back reflection.
• Optical isolator is a passive optical device with high light transmittance in one direction and a high attenuation in an opposite direction. Almost all isolators in practical use are based on Faraday effect; here, the polarization of light is prevented from rotating reciprocally by using an external magnetic field. Besides, there are other and often more complex techniques that can be used for obtaining isolation.
• isolation is particularly important for high-power lasers wherein both the risk of damage and the adverse effect thereof are greater.
• it is difficult to obtain optical isolators and it becomes increasingly expensive to obtain at higher powers.
• the increase of the output power of lasers is due to the increase of the power of optical isolators. Therefore, an alternative and practical method is needed in order to obtain effective optical isolation without using an optical isolator device.
• the United States patent document no. US2019027888 discloses an apparatus and a method used for optical isolation.
• the apparatus comprises a laser, a beam delivery system, and an output port.
• the laser is defined by a peak power and it emits laser radiation at a signal wavelength.
• the laser radiation is coupled to the output port via the beam delivery system.
• the beam delivery system comprises an optical isolator and an optical fibre, and it attenuates the laser radiation at the signal wavelength such that the power of the laser radiation emitted by the laser is more than the power of the laser radiation at the output port.
• the optical isolator has greater backward optical isolation and greater forward transmission at the signal wavelength compared to the Raman wavelength.
• the optical fibre comprises a suppressing means for suppressing stimulated Raman scattering.
• the United States patent document no. US2014071518 discloses an optical isolator used for optically isolating an optical system.
• the optical isolator comprises a filter, and a Raman shifter.
• the filter is optically coupled with the output of the optical system, and filters back-reflected portions of the shifted frequencies electromagnetic radiation.
• the Raman shifter is optically coupled with the output of the filter for shifting the frequencies of the electromagnetic radiation through Raman scattering.
• the Chinese patent document no. CN101217227 discloses a protection isolation device of a pump source laser diode.
• the laser diode isolation protection device is configured to provide a section of crystal or fiber pigtail between a pump source laser diode and a laser medium, and the crystal or the fiber pigtail has a high penetration of the output laser wavelength of the laser diode.
• the working wavelength laser, the stimulated Raman scattering light and the ASE light generated by the laser medium, the pump source laser diode are isolated from the pump source which protects these from damage, improves the service life of the laser diode and reduces the cost.
• An objective of the present invention is to realize an optical isolation method for performing optical isolation by spectral filter and gain band.
• Another objective of the present invention is to realize an alternative and highly practical optical isolation method in order to obtain effective optical isolation without using an optical isolation device.
• a further objective of the present invention is to realize an optical isolation method which enables to overcome the reflection effect of the laser by using spectral filter.
• Figure l is a general view wherein graphics of a gain isolation mechanism are included.
• Figure 2 is experimental graphics of a) experiment (squares) and simulation (line) output power of the back-reflected light against the central wavelength; b) results of the amplified back reflection; c) simulated output power for 2W source and different back reflection powers of 100 mW (triangles), 200 mW (squares) and 300 mW (circles); and d) results of the amplified back-reflected power in the inventive optical isolation method.
• the inventive method (100) used for providing optical isolation comprises steps of:
• the width of the laser output spectrum is asymmetrically extended typically towards longer wavelengths, due to a wide variety of non-linear effects and in particular to Raman scattering (101).
• the central wavelength switches to a longer wavelength.
• the wavelength switches from 1030 nm to 1150 nm.
• the long-pass filter cuts the wavelength in the gain bandwidth range (A) and passes the rest of the spectrum (102).
• the laser output is sent to the target (H) (103).
• Part of the laser beam is sent to the laser again (104), due to back reflection.
• This beam is stopped by the spectral filter partly (105). Too little or no gain is obtained because the laser beam part escaping from the filter does not comply with the gain bandwidth of the laser (105). Therefore, the fiber or the optical medium wherein the original spectral shift occurs plus the gain band and/or the spectral filter protect the laser system by acting as an isolator entirely (105).
• optical isolation method (100) it is ensured to successfully protect a laser against back reflection without natural limitations and high costs, as in optical isolator.
• Preliminary experiments conducted about the method (100) are carried out by 10 W ytterbium (Yb)-doped laser.
• Back reflection and amplified back reflection powers are measured by power meters simultaneously.
• the central wavelength of the back reflected laser may disrupt the output power if it is within the gain bandwidth as shown in the Figure 2a.
• isolation is obtained over 20 dB by filtering the spectrum within the gain bandwidth as shown in the Figure 2b.
• the method (100) is verified by the simulation results shown in the Figure 2c and the Figure 2d.

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Optics & Photonics (AREA)
• Lasers (AREA)
• Optical Filters (AREA)
• Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 2019
  • 2019-12-30 TR TR2019/22541A patent/TR201922541A2/tr unknown
• 2020
  • 2020-12-22 WO PCT/TR2020/051353 patent/WO2021137810A1/en not_active Ceased
  • 2020-12-22 EP EP20910176.5A patent/EP4085301A4/de not_active Withdrawn

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