The quality of beam produced by a Q-switched Neodymium: YAG optical maser was investigated. A photographic technique associated with image processing system was utilized to find the beam quality. The unseeable visible radiation was detected utilizing burn paper at assorted operation electromotive forces of flashlamp driver in the scope of 450 V to 900 V. The lasting record of the beam musca volitanss were made via a scanner and analyze utilizing raster in writing or electronic image from a Matrox Inspector version 2.1 package. The line profile each of the beam topographic point produced an soaking up spectrum. The amplitude of the spectrum indicates the depthness of the hole created after optical maser interaction with photographic paper. Meanwhile the breadth shows the beam size every bit good as the surface raggedness. Thus the beam quality is illustrated by the depthness and the two-dimensionality of the beam topographic point. The flatter the surface the more unvarying the optical maser beam distribution and the deeper the hole the more energetic the optical maser beam interacted with burn paper.
Neodymium: YAG optical masers can be operated in both pulsed and uninterrupted manner. The pulsed optical masers are typically operated utilizing Q-switching mechanism: In Q-switched manner, the optical maser end product powers of 20 megawatts graduated table and pulse continuances of less than 100 nanoseconds are normally available. The high-intensity pulsations may be required to change over visible radiation from 1064 to go 532 nm through the procedure of frequence doubler, or even higher order harmonics coevals can be achieved at 355 and 266 nm [ 1 ] . A high quality beam is desired to pump another high power optical maser such terawatt category Ti: Sapphire amplifiers [ 2 ] .
The M2 factor normally uses to qualify the quality of the optical maser beam [ 2-3 ] . However the M2 factor being a individual figure and can non be considered as a complete word picture of beam quality. The existent quality of a beam could be estimated by utilizing beam profiler or CCD camera [ 4 ] and phosphor stuff [ 5 ] . However, the low cost, fast and simple technique to mensurate the beam quality could be achieved by utilizing photographic paper or burn paper [ 5 ] . When the unfocussed optical maser beam interacts with this stuff, the vaporisation occurred ; atoms take and the taint was observed. By utilizing this technique, the beam topographic point of the optical maser could for good enter.
In this paper, the beam quality of Q-switched Nd: YAG optical maser was characterized based on the soaking up on burn paper. The line profiles of the beam topographic point at different energies were analyzed utilizing raster graphic or electronic image.
A RASTER GRAPHIC
Assumed that the optical maser beam propagates in the Gaussian & A ; acirc ; ˆ™s beam profile. After optical maser interacts with a mark stuff ( in this instance photographic paper ) the beam topographic point was considered to be in the signifier of aired disc. The strength profile of such aired disc will be transform into Gaussian beam as illustrate in the raster graphic or electronic image such as shown in Figure 1. A electronic image is technically characterized by the breadth and tallness of the image in pels and by the figure of spots per pel.
Signing or index related to the consequence of soaking up on the burn paper. The amplitude or the tallness of the Gaussian profile in Figure 1 is besides indicated the depthness of the hole created on the burn paper. The beam size can be determined based on the breadth of the Gaussian beam profile. Raster artworks are resolution dependant. In this work, the declaration can be achieved up to 1 centimeters:
Figure 1: The relationship between deepness and beam size of the beam topographic point.
In this experiment a developed Q-switched Neodymium: YAG optical maser was employed as beginning of visible radiation. The cardinal wavelength of the optical maser is 1064 nanometer. The optical maser was Q-switched Nd: YAG utilizing KD*P as a Pockels cell. The quarter-wave electromotive force of the q-switched driver was 3.0 kilovolt. The pulse continuance of the Q-switched optical maser was 10 N. The optical maser was operated in a individual pulsation operation. The power of the optical maser was regulated by altering the capacitance electromotive force between 500 V and 900 V.
Exposed IFord Photographic paper was used as a burn paper. The burn documents were cut into 100s pieces. Each piece was used to observe a individual exposure from unseeable infrared optical maser beam. The unfocussed optical maser beam was exposed on the burn paper. The paper was placed at an indistinguishable location. Assorted exposures were produced by seting the capacitance electromotive force of the flashlamp driver. For each changeless electromotive force, the beam topographic point will be obtained 10 times. The norm of 10 read out will stand for the size of beam topographic point.
The image of the beam topographic point for each electromotive force was for good recorded by scanning utilizing HP Scan Jet 2300. The file was saved and reassign into personal computing machine for farther analysis. Matrox Inspectors version 2.1 was utilized to analyse the raster graphic of the beam topographic point. The tallness and the breadth are measured in arbitrary units ( arb. unit ) . The whole experimental set-up is shown in Figure 2.
Figure 2: Experimental Setup of beam quality measuring.
RESULT AND DISCUSSION
The unfocussed beam of infrared ( IR ) optical maser ( 1064 nanometer ) was detected utilizing burn paper. The paper was instantly damaged when interacted with an energetic optical maser beam. Figure 3 shows the typical beam musca volitanss for both Q-switched and pulsed Nd: YAG optical maser at 700 V of electromotive force operation. From the experiment, for pulsed optical maser operation ( without Q-switched ) , the threshold energy to bring forth the beam topographic point on the burn paper is 50 mJ. Meanwhile the threshold energy for Q-switched optical maser is 10 mJ. The difference between pulsed and Q-switched optical maser beam topographic point could be recognized utilizing bare eyes. For Q-switched pulsation, the colour of the beam topographic point is brighter, unvarying and solid unit of ammunition form as compared to pulsed optical maser such as depicted in Figure 3.
( a ) Pulsed
( B ) Q-switched
Figure 3: Beam topographic point on burn paper at 700 V of operation electromotive force ( a ) free running optical maser, ( B ) Q-switched Neodymium: YAG optical maser.
For farther analysis of beam quality, the line profile option from matrox inspector version 2.1 package was performed. On the right manus side of Figure 3 shows the profile of beam soaking up for both free running pulsed and Q-switched optical maser. The spectrum of free running pulsed and Q-switched optical maser is evidently different. For free running pulse optical maser, the spectrum consisting several crisp extremums. The assorted extremums represent the irregular raggedness of the surface. In mean the deepness of the hole created on the burn paper is quantified to be as 60 arbitrary units ( Figure 3a ) . In contrast, the soaking up spectrum of beam topographic point for Q-switched optical maser shows merely a individual extremum with a level top. This indicates that the surface of the beam topographic point is smooth due to the impact of unvarying light distribution on the burn paper. The tallness of the extremum is tantamount with the deepness of hole drilled by the Q-switched optical maser. In mean the deepness is 100 arbitrary units which is 40 % better than produced by pulsed optical maser. From this observation, the beam quality is measured base on the soaking up spectrum. The two-dimensionality of the spectrum extremum becomes the measuring of the beam quality. The best beam quality is based on the uniformity and the energetic of the visible radiation. This is transformed on the beam topographic point form. The two-dimensionality of the extremum means the smoothness of the surface, indirectly indicates that uniformity of the optical maser beam distribution. The strength or the energetic of the optical maser beam is illustrated by the deepness or the tallness of the extremum. The higher the extremum means the deeper the drilled hole on the burn paper.
The old guess was confirmed by look intoing assorted operation electromotive force of the flashlamp power supply. The typical consequences obtained from these experiments are depicted in Figure 4. The beam musca volitanss are arranged in the increasing order of the operation electromotive force. Each beam topographic point, associated with its ain line profile. Irregular extremums are observed in Figure 4 ( a ) and Figure 4 ( vitamin E ) indicate that the non-uniformity of light distribution impact on the burn paper. The soaking up spectrum as shown in Figure 4 ( B ) about similar to the Gaussian beam profile. This is occurred at operation electromotive force of 600 V. The beam quality of the optical maser is about similar as uniphase of cross electromagnet TEMoo. The beam topographic point about like an aired disc, holding deep portion in the centre and shallow portion upward. This translates that the denseness of beam image whereby the brightest at the centre and acquiring blurred as it propagates outward. This quality is merged with M2 definition, whereupon it depends on the quality of the beam to be focused. To run into the definition, intend this optical maser demand to be operated at 600 V.
As the optical maser operated with higher operation electromotive forces, the beam topographic point becomes solid and concentrated. This is demonstrated such as shown in Figure 4 ( degree Celsius ) and Figure 4 ( vitamin D ) matching to operation electromotive force of 700 V and 800 V. The image of beam topographic point is manifested in solid round constellation. The line profile of such solid surface demonstrated the concentrated spectrum of soaking up. The impregnation is demonstrated by the level top of the extremum, similar as if the beam directed detected by the photodiode. Due to the super-radiation of the visible radiation, the photodiode become overexposure, and expose a concentrated signal. Similar constellation is observed on the burn paper, no more aired disc form, but the smoothness surface as shown with the level top. In contrast, this can be as an index that the homogeneous distribution of photon impact on the burn paper. As a consequence the quality of beam green goods at this high terminal of the operation electromotive force is really energetic and uniformity. Hence, with high power operation optical maser, the best beam quality is represented by the solid round constellation of beam topographic point associated with homogeneous level top of soaking up spectrum. Meanwhile at the low terminal operation electromotive force, the beam quality can keep as aired disc formation which indicated the Gaussian beam profile.
a ) 500 V
B ) 600 V
degree Celsius ) 700 V
vitamin D ) 800 V
vitamin E ) 900V
Figure 4: Typical beam musca volitanss and line profile of Q-switched Nd: YAG optical maser at different operation electromotive force of power supply.
The electronic image of the soaking up spectrum were quantified based on the tallness and the breadth of the extremum. The tallness represents the deepness of the hole created on the burn paper. Meanwhile the breadth is stand foring the beam topographic point diameter. Figure 5, shows the relationship between the deepness and breadth with regard to the operation electromotive force. Both curves have non-linear relationship. Initially change occurs drastically, the deepness and the beam diameter addition suddenly upon the operation electromotive force. The burn paper instantly contaminate after interacted with Q-switched optical maser. The sensitiveness of the paper allows the combustion following the contour of the entrance beam. In extra, the shortest pulse continuance induced local warming without affected neighbouring countries. As a consequence, the beam topographic point follow precisely the cross subdivision of beam radiation. Although the heat is non conduct laterally, but the beam does penetrated through the documents. The photographic paper comparatively thicker as compared to the normal A4 paper, so the incursion is allowable depends on the energetic of the entrance beam. The higher the energy the deeper the beam penetrated under the paper. In general the deepness of beam topographic point due to operation electromotive force in between 400 V to 500 V, is found to be 90 arbitrary unit. The deepness is so increased bit by bit against the operation electromotive force. The optimal deepness of 120 arbitrary is obtained at operation electromotive force of 750 V. At higher operation electromotive force of 900 V, the deepness is found to be 100 arb. units. The possible ground for the decreasing is due to the fluctuation or un-stability of the optical maser end product at higher operation electromotive forces. The beam diameter profile is similar tendency as deepness profile. Except that no important beam size is realized, since the size is about consistent.
Figure 5: The norm of deepness of hole created on photographic paper for operation electromotive force from 450 to 900 Volts
The beam quality of infrared optical maser is determined based on the soaking up spectrum of photographic paper. Burn paper is the easiest manner to observe the being of unseeable visible radiation of Nd: YAG optical maser. Furthermore the sensor can besides extended to go as a examiner for the beam quality of high power optical maser. The consequence of immediate soaking up on burn paper is analyzed based on raster graphic or electronic image. As a consequence the beam quality is found to be similar as Gaussian beam profile for low operation electromotive force ( 600V ) . Smoothen level top and deep incursion due to concentrated soaking up is identified as the best beam quality for high operation electromotive force of 700V.