Laser Exciting of Bound Photonic States and High Frequency Gravitational Waves in Media during Combinational Light Processes

Multiple Stokes and anti-Stokes satellites (Comb Parametric Raman Processes) were observed in liquids and crystals when excited by picosecond laser pulses of a YAG:Nd3+ solid-state laser with generation wavelengths of 1064 and 532 nm. The Stokes combination satellites of the infrared range were detected as a result of their conversion into the visible spectral region. The bound two-photonic states, corresponding to high frequency gravitational waves, in media due to strong photon-photon interactions is predicted.


Introduction
After the appearance of intense laser light sources, the phenomenon of stimulated Raman scattering (SRS) of light in various dielectric media was discovered [1,2]. In contrast to spontaneous Raman scattering (RS), in spectrum of SRS a sharp increase in the intensity of one of the strongest spontaneous Stokes RS line was observed. With a further increase of the spectral intensity of the exciting laser radiation, the several Stokes and anti-Stokes satellites in liquids or crystals appear. Its intensity becomes close to the intensity of the exciting laser radiation [2][3][4]. Thus Combinational Parametric Raman Scattering (CPRS) processes take place. In this case the simultaneous destruction of two quanta of exciting radiation and Stokes and anti-Stokes pairs birth [5][6][7] is realized. At the first stage of SRS researches the giant pulses of ruby or yttrium aluminum garnet lasers with a duration of about 10 ns and sufficiently high energy in each pulse (0.1-1 J) as the source of exciting light have been used. When such radiation was strongly focused on a dielectric medium, the destruction of the the samples took place, preventing the possibilities of CPRS observing in many media. Recently multi-frequency Raman scattering processes were observed in many liquids [8,9] and crystals [10][11][12] under picosecond laser emission.
Parametric excitation of high frequency gravitational waves in cosmic objects has been predicted in several works [13][14][15][16]. We have analyzed the opportunity to observe the resemble effect in dielectric media on the base of CPRS. If the frequency of exciting laser emission is ω 0 , the creation of scalar bound two-photonic state with frequency (2ω 0 ) in dielectric media is waiting. Such bound states correspond to high frequency scalar gravitational wave. The conditions for bound two-photonic states appearing in dielectric media are the strong photon-photon interaction by means of virtual phonons exchange between interacting photons during CPRS. High quality Q-factor bound two-photonic states may exist at the presence of Fermi Resonance. In this case, the scalar exciton states with energy, close to the bound two-photonic states with frequency are located in spectra of media. Elementar excitations of vacuum, corresponding to bound two-photonic states, is known as paraphotons or hidden photons [17][18][19][20]. For detection of high frequency scalar gravitational waves, i.e paraphotons, the same media, in which bound two-photonic states were excited, should be used.
In this paper the experimental results of CPRS spectra recording in various condensed dielectric media (CaCO 3 , quartz, NaBrO 3 , Ba(NO 3 ) 2 and others), excited by ultra short (60-80 ps) YAG:Nd 3+ laser pulses, are presented. The different experimental schemes for the generation and detection of scalar high frequency gravitational waves and paraphotons during CPRS is discussed

Experimental technique
The investigations of CPRS processes in various condensed dielectric media excited by ultrashort (60-80 ps) YAG:Nd 3+ laser pulses have been made. The second optical harmonic of a YAG:Nd 3+ laser with an emission wavelength λ = 532 nm and the main generation line of this laser with a wavelength λ = 1064 nm for the excitation of the SPRS spectra in crystals ( Figure 1) and liquids ( Figure 2) have been used. Figure 1. Schematic diagram of an experimental setup for recording the SPRS spectra in condensed media when the second optical harmonic of a YAG:Nd 3+ laser is excited (λ = 532 nm); 1 -YAG:Nd 3+ laser; 2 -lens; 3 -nonlinear optical crystal; 4 -laser emission; 5 -fiber tip; 6 -quartz fiber; 7 -mini spectrometer; 8 -computer.

Experimental results and discussion
Liquids (light and heavy water, ethanol, glycerin) and single crystals (barium nitrate, calcite, sodium bromate, KGW) as well as crystalline powders (LiOH, LiOD) were investigated. Equidistant frequency combs were detected in the form of a large number (2)(3)(4)(5)(6)(7)(8) of Stokes and anti-Stokes satellites, extending from the far infrared region to the ultraviolet range (see Figure  3, a-f). In accordance with the synchronization conditions for the elementary processes of the four-particles SPRS, the energy and quasimomentum conservation laws must be satisfied. In the simplest case of the decay of two quanta of exciting radiation into the corresponding Stokes and anti-Stokes components, we have: The conditions of synchronism for another processes take the form: The SPRS was observed in ethanol by pumping radiation from a second-harmonic of a YAG:Nd 3+ laser (see Figure 3(a,b)). For the "forward scattering" (see Figure 3a), one anti-Stokes and two Stokes lines were recorded with an average frequency shift is ∆ν = 2923 cm −1 . From Figure 3(a), it can be seen that the half width of the blue anti-Stokes mode is much larger than that of the first and second Stokes lines. The registration of the SPRS spectrum with the reflection (backward scattering) geometry (see Figure 3(b)) leads to a change in the number and shape of the observed lines. The first Stokes line in Figure 3(b) has more half width than in Figure 3(a) as a result of the formation of a two-component band with frequencies of 2836 and 2921 cm −1 instead of one narrow line at a frequency of 2947 cm −1 (see Figure 3(a)). On both sides of the high-intensity first and second Stokes satellites, the low intensity wings were detected (see Figure 3 (b)).
Excitation of the calcite single crystal by laser radiation with a wavelength of λ = 532 nm leads to the generation of SPRS with four Stokes and three anti-Stokes Raman satellites in the visible and near-infrared ranges (see Figure 3(c,d)). All observed lines belong to the full-dimensional oscillation A 1g with a frequency shift ∆ν = 1086 cm −1 .
When a SPRS was excited in a Ba(NO 3 ) 2 crystal by a picosecond pulsed YAG:Nd 3+ laser with a pump wavelength of λ = 1064 nm, a large number of combinational satellites were recorded (see Figure 3(e,f)), located in a wide spectral range, in the near IR and visible regions of the spectrum. According to Figure 3(e,f) in the spectrum of multifrequency SPRS in barium nitrate crystal, the eight anti-Stokes components appeared with the frequency shift ∆ν = 1047 cm −1 (taking into account the measurement error of ±50 cm −1 ). This corresponds to fully symmetric  internal vibrations of nitrate ions [NO 3 ]. In multifrequency SPRS processes, each anti-Stokes component (see Figure 3(e,f)) corresponds to some Stokes satellite, placed in the infrared region of the spectrum. Figure 4 shows the SPRS spectra of barium nitrate and glycerol obtained during the experiment on a device with a frequency doubler of scattered radiation The spectrum of SPRS of barium nitrate in Figure 4 of the passage of secondary radiation through a crystal -a frequency doubler.
As a result, modes were detected corresponding to twice the frequencies of the first (ν = 7250 cm −1 ) and the second (ν = 5170 cm −1 ) Stokes lines, which are in the infrared region. As a result of the scattered radiation passing through the frequency doubler, additional combination satellites are formed, corresponding to the combination of exciting radiation with the first Stokes line (ν = −8282 cm −1 ) and the sum of the frequencies of the first and second Stokes (ν = −6208 cm −1 ) components of the spectrum. Figure 4(b) shows the spectrum of the SPRS of glycerol with the conversion of the first Stokes (ν = −6448 cm −1 ) component to the red region of the visible range. Thus, the SPRS satellites have been registered from the IR range.
The excitation of a large number of Stokes and anti-Stokes components (see Figure 3) when pumping single crystals and liquids with ultrashort pulsed laser radiation in the visible and near infrared ranges provides the possibility of obtaining lasing frequency bands in a wide spectrum: from far infrared to ultraviolet. Spare biphoton Stokes-antiStokes states, emerging during SPRS, may be transformed into bound photonic states. Such result is predicted by the theory [21,22] under conditions of the strong photon-phonon interaction, if the frequency of exciting laser emission is ω 0 , the created scalar bound two-photonic state is described as scalar gravitational  Figure 5. Schematic diagram of an experimental setup for recording of high frequency gravitational waves in the case SPRS processes in crystals; 1 -YAG:Nd 3+ laser, 2 -lenses, 3 -nonlinear crystal; 4 -laser emission; 5 -opaque stopper, 6 -fiber tip, 7 -quartz fiber; 8 -mini spectrometer; 9 -computer. Figure 6. Schematic diagram of an experimental setup for recording of high frequency gravitational waves in the case SPRS processes in liquids; 1 -YAG:Nd 3+ laser, 2 -lenses, 3 -nonlinear liquids; 4 -laser emission; 5 -opaque stopper, 6 -fiber tip, 7 -quartz fiber; 8 -mini spectrometer; 9 -computer. wave with frequency 2ω 0 . Thus in this nonlinear processes the high frequency gravitational waves may be excited in dielectric media. The preferable conditions for bound two-photonic states existence are the Fermi resonance presence. In this case, the scalar exciton states with energy, close to the bound two-photonic states with frequency 2ω 0 , are in electronic spectra of media. After bound two-photonic states creating in media due to pulsed laser excitation, the corresponding scalar gravitational waves should propagate in vacuum (spare space). Elementar excitations of such waves is known as paraphotons or hidden photons. For detection of high frequency scalar gravitational waves, the same media (in which bound two-photonic states were excited) is proposed in the experimental schemes, presented at Figures 5,6.

Conclusion
The experimental results of investigations of CPRS in various condensed dielectric media (CaCO 3 , quartz, NaBrO 3 , Ba(NO 3 ) 2 and others), excited by ultra short (60-80 ps) YAG:Nd 3+ laser pulses, are presented. The second optical harmonic of a YAG:Nd 3+ laser with wavelength λ = 532 nm as well as the laser emission with a wavelength λ = 1064 nm were very effective for the excitation of the CPRS spectra in discussed dielectric media. The opportunity of high frequency gravitational wave generation and detection in dielectric media was analyzed.