Abstract:
Technologies are described for methods and systems effective to compress an input pulse to produce an output pulse. The methods may include receiving, by a pulse compressor, the input pulse. The methods may further include producing, by the pulse compressor, an unchirped portion of the input pulse. The methods may further include producing, by the pulse compressor, a chirped portion of the input pulse. The methods may further include filtering out, by the pulse compressor, the unchirped portion. The methods may further include compressing, by the pulse compressor, the chirped portion to produce the output pulse.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application 62/021,725 filed on Jul. 8, 2014, the entire contents of which are incorporated herein by reference. 
     
    
     STATEMENT OF GOVERNMENT RIGHTS 
       [0002]    The present application was made with government support under contract numbers DE-AC02-98CH10886 and DE-SC0012704 awarded by the U.S. Department of Energy. The United States government has certain rights in the invention. 
     
    
     FIELD OF THE INVENTION 
       [0003]    This disclosure relates generally to a laser pulse compressor. 
       BACKGROUND 
       [0004]    A pulse may be compressed from a first duration to a second duration that may be less than the first duration. An intensity of the pulse may also increase as a result of the compression of the pulse. Compression of ultra-short pulses may lead to undesirable effects such as self-focusing, limited compressibility, instability in the compressed pulse, etc. 
       SUMMARY 
       [0005]    In some examples, a pulse compressor is generally described. The pulse compressor may include a transmission medium. The transmission medium may be effective to receive an input pulse, produce an unchirped portion of the input pulse and produce a chirped portion of the input pulse. The pulse compressor may further include a spatial filter in operational relationship with the transmission medium. The spatial filter may be effective to receive the chirped portion and unchirped portion and filter out the unchirped portion. The pulse compressor may further include a collimator in operational relationship with the spatial filter. The collimator may be effective to receive and collimate the chirped portion to produce a collimated pulse. The pulse compressor may further include a compressing device in operational relationship with the transmission medium, the spatial filter, and the collimator. The compressing device may be effective to receive and compress the collimated pulse to produce an output pulse. 
         [0006]    In some examples, methods for compressing a pulse are generally described. The methods may include, by a device, receiving an input pulse. The methods may further include producing an unchirped portion of the input pulse. The methods may further include producing a chirped portion of the input pulse. The methods may further still include filtering out the unchirped portion. The methods may include compressing the chirped portion to produce an output pulse. 
         [0007]    In some examples, a device is generally described. The device may include a transmission medium being effective to receive an input pulse, produce an unchirped portion of the input pulse, and produce a chirped portion of the input pulse. The device may further include a spatial filter in operational relationship with the transmission medium. The spatial filter may be effective to filter out the unchirped portion of the input pulse, and output the chirped portion of the input pulse. 
         [0008]    The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0009]    The foregoing and other features of this disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings, in which: 
           [0010]      FIG. 1  illustrates a system drawing of a pulse compressor; 
           [0011]      FIG. 2  illustrates a system drawing of an implementation of a pulse compressor; and 
           [0012]      FIG. 3  illustrates a flow diagram of an example process to implement a pulse compressor; 
           [0013]    all arranged according to at least some embodiments described herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. 
         [0015]    In  FIG. 1  a system is drawn illustrating a pulse compressor  100 , arranged in accordance with at least some embodiments presented herein. As discussed in more detail below, a pulse compressor  100  may include a transmission medium  102  in operational relationship with a spatial filter  104 . An input pulse  110  may propagate, such as for example from a light source, to pulse compressor  100 . An example of input pulse  110  may be an ultra-short pulse from a laser that is of a duration of less than approximately 1 nanosecond (ns). Pulse compressor  100  may perform compression on input pulse  110  to produce an output pulse  120 . Input pulse  110  may travel through compressor  100  such as propagating through mechanisms of compressor  100  during the compression of input pulse  110 . 
         [0016]    Pulse compressor  100  may include a transmission medium  102 , a spatial filter  104 , a collimator  106 , and/or a compressing device  108 . Transmission medium  102 , spatial filter  104 , collimator  106 , and/or compressing device  108  may be in operational relationship with each other. Transmission medium  102 , spatial filter  104 , and collimator  106  may be positioned relative to each other based on parameters of input pulse  110  (described below). Spatial filter  104  may be positioned between transmission medium  102  and collimator  106 . A distance between transmission medium  102  and spatial filter  104  may be based on parameters of input pulse  110 . A distance between spatial filter  104  and collimator  106  may also be based on parameters of input pulse  110 . 
         [0017]    Transmission medium  102  may be a non-linear dispersive medium such as for example a germanium window. Transmission medium  102  may have a refractive index, wherein the refractive index may include a linear component and a non-linear component. The refractive index may be based on a material composition of transmission medium  102 . As input pulse  110  propagates through transmission medium  102 , an unchirped portion  111  of input pulse  110  may be produced based on the linear component of the refractive index. Unchirped portion  111  may be a portion of input pulse  110  which propagates at a frequency that does not vary in time. 
         [0018]    Similarly, as input pulse  110  propagates through transmission medium  102 , a chirped portion  112  of input pulse  110  may be produced based on the non-linear component of the refractive index. Chirped portion  112  may be a result of self-phase modulation and/or self-chirping of input pulse  110 . Chirped portion  112  may be a portion of input pulse  110  which propagates at a frequency that varies in time. In some examples, chirped portion  112  may include a linearly chirped component  113  and may include a non-linearly chirped component  114 . Linearly chirped component  113  may be a portion of chirped portion  112  which propagates at a frequency that varies with time linearly. Non-linearly chirped component  114  may be a portion of chirped portion  112  which propagates at a frequency that varies with time non-linearly. 
         [0019]    Unchirped portion  111  and chirped portion  112  of input pulse  110  may propagate to spatial filter  104 . Spatial filter  104  may be effective to filter out unchirped portion  111  and may be effective to filter out non-linearly chirped component  114 . Spatial filter  104  may be effective to output the chirped portion  112  of the input pulse  110 . Spatial filter  104  may be a sheet of metal and may include a separation section  105 . In some examples, separation section  105  may be made of a transparent material. In some examples, separation section  105  may be an aperture formed by a wall  103 . As a result of the filtering by spatial filter  104 , chirped portion  112  may propagate through separation section  105 . In an example, focusing on a front view of spatial filter  104 , spatial filter  104  may include an area  105   a  which may be effective to block, absorb, or reflect unchirped portion  111  and non-linearly chirped component  114 . Filtering of unchirped portion  111  and non-linearly chirped component  114  may be based on a size of separation section  105 . The size of separation section  105  may be based on parameters of input pulse  110 , such as intensity, wavelength, frequency, energy, time duration, etc. 
         [0020]    Collimator  106  may include one or more lenses, such as a curved lens. In an example, collimator  106  may include a lens with a focal distance equal to a distance between spatial filter  104  and collimator  106 . As a result of propagation through collimator  106 , chirped portion  112  may be collimated to produce collimated pulse  114 . Collimated pulse  114  may include rays of chirped portion  112  where the rays propagate in parallel. Collimated pulse  114  may propagate to compressing device  108 . 
         [0021]    Compressing device  108  may be a grating compressor or a negative-dispersion window. Compressing device  108  may include more than one grating effective to diffract collimated pulse  114 . Compressing device  108  may be effective to compress collimated pulse  114  to produce output pulse  120 . Output pulse  120  may be a compressed variation of input pulse  110 . A time duration of output pulse  120  may be less than a time duration of input pulse  110 . A power of output pulse  120  may be greater than a power of input pulse  110 . 
         [0022]    In  FIG. 2  a system is drawn illustrating an example relating to an implementation of pulse compressor  100 , arranged in accordance with at least some embodiments presented herein.  FIG. 2  is substantially similar to system  100  of  FIG. 1 , with additional details. Those components in  FIG. 2  that are labeled identically to components. of  FIG. 1  will not be described again for the purposes of clarity. 
         [0023]    In an example, input pulse  110  may be a pulse from a carbon dioxide laser of a wavelength of 10-microns, time duration of 1.7 picoseconds, and energy of 70 Joules. Non-linear element  102  may be a germanium window of a thickness of two millimeters. A distance between non-linear element  102  and spatial filter  104  may be six meters. As a result of compression performed by pulse compressor  100 , output pulse  120  may be a pulse of time duration of 100 femtoseconds, and energy of 18 Joules. As shown by performance  210 , output pulse  120  includes a significantly higher power than input pulse  110 . Time duration of output pulse  120  is also significantly lower than the time duration of input pulse  110 . 
         [0024]    A system in accordance with the present disclosure may provide a method to compress ultra-short pulses in a more efficient manner. Laser beams with Gaussian intensity distribution can be compressed even if the beam undergoes self-focusing, where a refractive index of a transmission medium changes. Contributions from low intensity portions of the laser beam need not affect the ability of the compressor to compress the beam. Similarly, variations in intensity of input pulses need not affect the compressibility. 
         [0025]      FIG. 3  illustrates a flow diagram of an example process to implement a pulse compressor, arranged in accordance with at least some embodiments presented herein. The process in  FIG. 3  could be implemented using, for example, system  100  discussed above. An example process may include one or more operations, actions, or functions as illustrated by one or more of blocks S 2 , S 4 , S 6 , S 8 , and/or S 10 . Although illustrated as discrete blocks, various blocks may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the desired implementation. 
         [0026]    Processing may begin at block S 2 , “Receive an input pulse”. At block S 2 , a pulse compressor may receive an input pulse. In some examples, the input pulse may be an ultra-short pulse of an order less than 1 nanosecond. 
         [0027]    Processing may continue from block S 2  to block S 4 , “Produce an unchirped portion of the input pulse”. At block S 4 , the pulse compressor may produce an unchirped portion of the input pulse. Production of the unchirped portion of the input pulse may include propagating the input pulse through a non-linear transmission medium. In some examples, the non-linear transmission medium may be a germanium window. 
         [0028]    Processing may continue from block S 4  to block S 6 , “Produce a chirped portion of the input pulse”. At block S 6 , the pulse compressor may produce a chirped portion of the input pulse. Production of the chirped portion of the input pulse may include propagating the input pulse through the non-linear element. The chirped portion may include a linearly chirped component and a non-linearly chirped component. 
         [0029]    Processing may continue from block S 6  to block S 8 , “Filter out the unchirped portion”. At block S 8 , the pulse compressor may filter out the unchirped portion of the input pulse. The pulse compressor may perform the filtering based on a size of an aperture of a spatial filter. The pulse compressor may further filter out the non-linearly chirped component of the chirped portion of the input pulse. 
         [0030]    Processing may continue from block S 8  to block S 10 , “Compress the chirped portion to produce an output pulse”. At block S 10 , the pulse compressor may compress the chirped portion of the input pulse to produce an output pulse. The compressor may be one of a grating compressor or a negative-dispersion window. In some examples, prior to compressing the chirped portion, the collimator may collimate the chirped portion. 
         [0031]    While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.