The 26 reference contexts in paper V. Savitski G., В. Савицкий Г. (2015) “ИМПУЛЬСНЫЙ ВКР-ЛАЗЕР НА KGd(WO4)2: СУЖЕНИЕ ШИРИНЫ ЛИНИИ ИСПУСКАНИЯ // PULSED KGd(WO4)2 RAMAN LASER: TOWARDS EMISSION LINEWIDTH NARROWING” / spz:neicon:pimi:y:2015:i:1:p:18-25

  1. Start
    1189
    Prefix
    Introduction High average power pulsed lasers with a narrow (ideally – 0 fontName limited) emission linewidth are essential for LIDAR (LIght Detection And Ranging) applications
    Exact
    [1, 2]
    Suffix
    . For LIDAR, better range and velocity resolution require shorter pulses and narrower emission linewidths respectively [1]. Simultaneous shortening of laser pulse duration and narrowing of the corresponding emission linewidth require generation of transform-limited pulses.
    (check this in PDF content)

  2. Start
    1326
    Prefix
    Introduction High average power pulsed lasers with a narrow (ideally – 0 fontName limited) emission linewidth are essential for LIDAR (LIght Detection And Ranging) applications [1, 2]. For LIDAR, better range and velocity resolution require shorter pulses and narrower emission linewidths respectively
    Exact
    [1]
    Suffix
    . Simultaneous shortening of laser pulse duration and narrowing of the corresponding emission linewidth require generation of transform-limited pulses. A system with a high signal to noise ratio requires high average power [1], and, hence, high pulse energies or repetition rates.
    (check this in PDF content)

  3. Start
    1572
    Prefix
    Simultaneous shortening of laser pulse duration and narrowing of the corresponding emission linewidth require generation of transform-limited pulses. A system with a high signal to noise ratio requires high average power
    Exact
    [1]
    Suffix
    , and, hence, high pulse energies or repetition rates. Higher pulse energies are usually preferable since a high repetition rate limits the range of the LIDAR system [1]. Narrow linewidth high power lasers suitable for LIDAR applications are usually based on fiber master oscillator power amplifier (MOPA) technology [3–5].
    (check this in PDF content)

  4. Start
    1758
    Prefix
    A system with a high signal to noise ratio requires high average power [1], and, hence, high pulse energies or repetition rates. Higher pulse energies are usually preferable since a high repetition rate limits the range of the LIDAR system
    Exact
    [1]
    Suffix
    . Narrow linewidth high power lasers suitable for LIDAR applications are usually based on fiber master oscillator power amplifier (MOPA) technology [3–5]. On the other hand, conversion of the pump wavelength via stimulated Raman scattering (SRS) [6] in crystalline media adds more flexibility in terms of output wavelength [7–14].
    (check this in PDF content)

  5. Start
    1920
    Prefix
    Higher pulse energies are usually preferable since a high repetition rate limits the range of the LIDAR system [1]. Narrow linewidth high power lasers suitable for LIDAR applications are usually based on fiber master oscillator power amplifier (MOPA) technology
    Exact
    [3–5]
    Suffix
    . On the other hand, conversion of the pump wavelength via stimulated Raman scattering (SRS) [6] in crystalline media adds more flexibility in terms of output wavelength [7–14]. However, less work has been reported on emission linewidth narrowing in solid-state (non-fiber) Raman lasers.
    (check this in PDF content)

  6. Start
    2021
    Prefix
    Narrow linewidth high power lasers suitable for LIDAR applications are usually based on fiber master oscillator power amplifier (MOPA) technology [3–5]. On the other hand, conversion of the pump wavelength via stimulated Raman scattering (SRS)
    Exact
    [6]
    Suffix
    in crystalline media adds more flexibility in terms of output wavelength [7–14]. However, less work has been reported on emission linewidth narrowing in solid-state (non-fiber) Raman lasers.
    (check this in PDF content)

  7. Start
    2101
    Prefix
    Narrow linewidth high power lasers suitable for LIDAR applications are usually based on fiber master oscillator power amplifier (MOPA) technology [3–5]. On the other hand, conversion of the pump wavelength via stimulated Raman scattering (SRS) [6] in crystalline media adds more flexibility in terms of output wavelength
    Exact
    [7–14]
    Suffix
    . However, less work has been reported on emission linewidth narrowing in solid-state (non-fiber) Raman lasers. To the best of our knowledge there is no research targeting Raman linewidth narrowing in solid-state Raman lasers emitting in pulsed regime.
    (check this in PDF content)

  8. Start
    2515
    Prefix
    To the best of our knowledge there is no research targeting Raman linewidth narrowing in solid-state Raman lasers emitting in pulsed regime. Only recently, the effect of broadening of the fundamental emission linewidth on the effective Raman gain in Raman lasers was studied
    Exact
    [15]
    Suffix
    . In this paper a proof of concept demonstration of a narrow linewidth crystalline Raman laser operating in pulsed mode with high peak power is reported. The effect of narrow linewidth injection seeding at the Raman laser wavelength on the performance of the Raman laser is studied.
    (check this in PDF content)

  9. Start
    2955
    Prefix
    The effect of narrow linewidth injection seeding at the Raman laser wavelength on the performance of the Raman laser is studied. Experimental setup The Raman laser was built around a Ng-cut KGd(WO4)2 (KGW) crystal, giving a positive thermal lens
    Exact
    [16, 17]
    Suffix
    which simplifies the Raman laser cavity design. The crystal was 30 mm in length. The end faces were anti-reflection (AR) coated for 1 and 1,15 m (R < 0,1 %). The source of fundamental laser emission was a diode sidepumped Nd:LiYF4 (Nd:YLF) module emitting at 1047 nm and described in detail in [14].
    (check this in PDF content)

  10. Start
    3287
    Prefix
    The end faces were anti-reflection (AR) coated for 1 and 1,15 m (R < 0,1 %). The source of fundamental laser emission was a diode sidepumped Nd:LiYF4 (Nd:YLF) module emitting at 1047 nm and described in detail in
    Exact
    [14]
    Suffix
    . The Raman shift of 901 cm-1 (which corresponds to a shift of the fundamental wavelength from 1047 nm to 1156 nm) was selected by appropriate choice of the coatings of Raman laser mirrors.
    (check this in PDF content)

  11. Start
    3539
    Prefix
    The Raman shift of 901 cm-1 (which corresponds to a shift of the fundamental wavelength from 1047 nm to 1156 nm) was selected by appropriate choice of the coatings of Raman laser mirrors. An intracavity Raman laser configuration
    Exact
    [18–20]
    Suffix
    , shown in Fi- gure 1a, for wavelength conversion from 1 to 1,15 m was chosen. The cavities of the Nd:YLF laser and the KGW Raman laser were coupled using dichroic mirrors (DM: highly reflective (HR) at 1,1– 1,25 m, highly transmissive (HT) at 1 m).
    (check this in PDF content)

  12. Start
    5240
    Prefix
    mm) was designed to be stable against a thermal lens in the Nd:YLF rod with a focal length of ~ –150 mm or longer (the manufacturer specifies a focal length of –750 mm at maximum diode pump power), and, simultaneously, against a thermal lens in the KGW of 200 mm focal length or longer. The thermal lens in the KGW crystal results from the inelastic nature of Raman scattering
    Exact
    [21]
    Suffix
    . Our calculations indicate that the main factor, influencing the fundamental (TEM00) mode size of 1047 nm field in the Nd:YLF and KGW crystals is the thermal lens in the KGW. When the focal length of the thermal lens in the KGW crystal increases from 200 to 1000 mm, the TEM00 beam radius of the 1047 nm field increases from 190 to 345 m in the Nd:YLF and decreases f
    (check this in PDF content)

  13. Start
    6546
    Prefix
    Its angle with respect to the cavity axis was ~7° and was finely tuned to maximise the Raman laser output power. Transmittance of the etalon as a function of wavelength after double passing of the laser beam (T2), which was calculated using the equation in
    Exact
    [22]
    Suffix
    is shown in Figure 1b. The narrow linewidth (< 4 MHz FWHM) distributed-feedback (DFB) laser diode (Toptica photonics) emitted a single transverse and longitudinal mode at 1156,6 nm was used to injection-seed [23] the Raman laser via the reflection from the Fabry–Perot etalon.
    (check this in PDF content)

  14. Start
    6781
    Prefix
    The narrow linewidth (< 4 MHz FWHM) distributed-feedback (DFB) laser diode (Toptica photonics) emitted a single transverse and longitudinal mode at 1156,6 nm was used to injection-seed
    Exact
    [23]
    Suffix
    the Raman laser via the reflection from the Fabry–Perot etalon. It has a maximum power of 12 mW (being attenuated down to 3 mW after passing through the isolator and waveplates, see Figure 1a), and could be tuned from 1155–1157 nm.
    (check this in PDF content)

  15. Start
    9014
    Prefix
    All the results presented below were obtained at this frequency. The reduced pulse energy of the Nd:YLF laser at frequencies below ~3 kHz is probably due to either amplified spontaneous emission or parasitic lasing
    Exact
    [24]
    Suffix
    . Figure 2 – Output energies of fundamental (1047 nm) and Raman (1156 nm) lasers as a function of Q-switching frequency The performance of the KGW Raman laser was analyzed in five configurations: i) No linewidth control of the fundamental or Raman emission (VBG-, FP-); ii) Fundamental emission linewidth control with a VBG, no Raman emission linewidth narrowi
    (check this in PDF content)

  16. Start
    15370
    Prefix
    Figure 5 – Fundamental (a) and Raman (b) lasers wavelengths as functions of incident diode pump power for the different cavity configurations Discussion The presence of the VBG in the fundamental laser cavity moves the emission peak towards longer wavelengths, as shown in Figure 5a. The gain bandwidth in Nd:YLF crystal is ~ 1,35 nm
    Exact
    [25, 26]
    Suffix
    . Therefore, it may be that the pulse energy at 1047 nm is lower with the VBG in the cavity due to a shift of the laser emission wavelength away from the Nd:YLF gain peak. Besides, the lower reflectivity of the VBG element (99,9 % at 1047 nm) compared to the HR mirror (< 99,99 %) is likely to have further decreased the intracavity pulse energy at 104
    (check this in PDF content)

  17. Start
    16220
    Prefix
    The slope efficiency of the Raman laser, nevertheless, remains the same (3,3 %) as it is mainly determined by the Raman laser output coupler reflectivity and passive losses in the Raman cavity
    Exact
    [27]
    Suffix
    . This in turn explains the slightly lower slope efficiency of 3 % and higher threshold (36 W) for the Raman laser in configuration iii) (VBG–, FP+), where the FP filter introduces additional losses to the Raman cavity.
    (check this in PDF content)

  18. Start
    17593
    Prefix
    The VBG reduces the intracavity pulse energy at the fundamental wavelength of 1047 nm, thus reducing the overall Raman gain in the Raman laser (which is proportional to a product of the Raman gain, pump intensity and the Raman crystal length
    Exact
    [28]
    Suffix
    ), while FP filter in the Raman cavity introduces additional losses for the Raman emission, similar to the configuration iii). The lower threshold of the Raman laser (33 W) in configuration v) (VBG+, FP+ with injection seeding) compared to configuration iv) without seeding (35 W) results from the fact that the Raman field need no longer build up from noise [
    (check this in PDF content)

  19. Start
    18050
    Prefix
    The lower threshold of the Raman laser (33 W) in configuration v) (VBG+, FP+ with injection seeding) compared to configuration iv) without seeding (35 W) results from the fact that the Raman field need no longer build up from noise
    Exact
    [28]
    Suffix
    . Without the seed, the Raman noise originates from the spontaneous Raman scattering and its intensity is significantly lower than that of the seed. The higher stability of the Raman wavelength in the configurations with the FP etalon (0,01– 0,02 nm) in comparison with that without the etalon and only with the VBG in the fundamental laser cavity (0,06 nm), Figure 5b, can be
    (check this in PDF content)

  20. Start
    18684
    Prefix
    (0,01– 0,02 nm) in comparison with that without the etalon and only with the VBG in the fundamental laser cavity (0,06 nm), Figure 5b, can be explained by the narrower filter function of the FP than that of the VBG, and the higher sensitivity of the Raman laser to losses due to lower gain in comparison with the fundamental laser. The theory of SRS
    Exact
    [29–32]
    Suffix
    predicts that in the case of a single-mode (monochromatic) fundamental, where the fundamental linewidth is significantly narrower than the spontaneous Raman linewidth of a crystal (i.e. tends to zero), one should observe socalled gain-narrowing of the Raman laser linewidth with respect to the spontaneous Raman linewidth.
    (check this in PDF content)

  21. Start
    19184
    Prefix
    linewidth is significantly narrower than the spontaneous Raman linewidth of a crystal (i.e. tends to zero), one should observe socalled gain-narrowing of the Raman laser linewidth with respect to the spontaneous Raman linewidth. This narrowing is inversely proportional to the square root of the fundamental intensity and can be as high as 6 at the threshold for SRS
    Exact
    [28, 29, 33]
    Suffix
    . In contrast, when the fundamental linewidth is significantly broader than the spontaneous Raman linewidth of a crystal, the linewidth of the Stokes emission of the Raman laser will tend to be as broad as that of the fundamental [30, 34].
    (check this in PDF content)

  22. Start
    19460
    Prefix
    In contrast, when the fundamental linewidth is significantly broader than the spontaneous Raman linewidth of a crystal, the linewidth of the Stokes emission of the Raman laser will tend to be as broad as that of the fundamental
    Exact
    [30, 34]
    Suffix
    . The latter case can be illustrated by a practical example [35] where intracavity pumping of a BaWO4 Raman crystal (with the narrow Raman linewidth of 1,6 cm-1) with a fundamental laser of linewidth of 1,77 cm-1 led to a Raman laser emission linewidth of 1,12 cm-1 at the Raman threshold (increasing to 3,74 cm-1 at higher pump powers).
    (check this in PDF content)

  23. Start
    19526
    Prefix
    In contrast, when the fundamental linewidth is significantly broader than the spontaneous Raman linewidth of a crystal, the linewidth of the Stokes emission of the Raman laser will tend to be as broad as that of the fundamental [30, 34]. The latter case can be illustrated by a practical example
    Exact
    [35]
    Suffix
    where intracavity pumping of a BaWO4 Raman crystal (with the narrow Raman linewidth of 1,6 cm-1) with a fundamental laser of linewidth of 1,77 cm-1 led to a Raman laser emission linewidth of 1,12 cm-1 at the Raman threshold (increasing to 3,74 cm-1 at higher pump powers).
    (check this in PDF content)

  24. Start
    20063
    Prefix
    The present experimental research deals with the intermediate case, when the pump linewidth is not significantly narrower than the Raman li- newidth (which is 5,4 cm-1 in KGW crystal at 901 cm-1 Raman frequency
    Exact
    [36]
    Suffix
    ). Experimental data indicate that in this case, when no special narrowing elements are put in both fundamental and Raman laser cavities, the Raman laser emission linewidth at Raman threshold is close to that of the fundamental emission (Figure 4a) similar to experimental results in [35].
    (check this in PDF content)

  25. Start
    20398
    Prefix
    Experimental data indicate that in this case, when no special narrowing elements are put in both fundamental and Raman laser cavities, the Raman laser emission linewidth at Raman threshold is close to that of the fundamental emission (Figure 4a) similar to experimental results in
    Exact
    [35]
    Suffix
    . Separate insertion of the emission linewidth narrowing element into either only the fundamental laser cavity or only the Raman laser cavity, in case of a KGW crystal, does not lead to any substantial narrowing of the Raman emission linewidth, especially at pump powers above the threshold (Figure 4).
    (check this in PDF content)

  26. Start
    21539
    Prefix
    Raman laser starts to oscillate in multi-transverse mode regime at high pump powers, thus leading to increased angle of incident of the Raman beam into the FP etalon due to the increased divergence of the Raman laser beam. Raman laser in this case oscillate on adjacent etalon modes, corresponding to diffe- rent angles of incident to the FP filter
    Exact
    [37]
    Suffix
    , which results in broadening of the Raman emission. In the case of a KGW Raman crystal one should aim for linewidth narrowing elements being put into both fundamental and Raman laser cavities in order to observe substantial narrowing of the Raman laser emission, even at high pump powers.
    (check this in PDF content)