Passive Q-switch laser

Abstract

A passive Q-switch for a laser system, and a method for its production. The laser is operative at near infrared wavelength region, including the eye-safe region. The Q-switch includes a saturable absorber based on IV-VI semiconductor nanocrystals (NCs), embedded in a polymer matrix. The NCs preferably include lead selenide, lead sulfide, or lead selenide sulfide. The NCs may be surface passivated, and may feature a PbSe/PbS core-shell configuration.

1 - 79 . (canceled)  
     
     
         80 . A passive Q-switch for a laser system operative at the ncar infrared wavelength region of 700-4,000 nm, said passive Q-switch comprising a saturable absorber comprising IV-VI semiconductor nanocrystals (NCs) embedded in a transparent matrix.  
     
     
         81 . A passive Q-switch according to  claim 80 , wherein said NCs comprise lead sclenide (PbSe).  
     
     
         82 . A passive Q-switch according to  claim 80 , wherein said NCs comprise lead sulfide (PbS).  
     
     
         83 . A passive Q-switch according to  claim 80 , wherein said NCs have a passivated surface.  
     
     
         84 . A passive Q-switch according to  claim 83 , wherein said NCs are surface passivated with organic ligands.  
     
     
         85 . A passive Q-switch according to  claim 83 , wherein said NCs are passivated by capping of organic molecules to their surface, wherein said organic molecules are selected from the list consisting of tributylphosphine (TBP), trioctylphosphine (TOP), TOP-oxide (TOPO), oleic acid, amines, and thiols.  
     
     
         86 . A passive Q-switch according to  claim 80 , wherein said NCs comprise core-shell semiconductor NCs, wherein said NCs comprise cores coated by semiconductor shells having an energy band gap wider than that of the core material.  
     
     
         87 . A passive Q-switch according to  claim 86 , wherein said cores comprise lead selenide (PbSc).  
     
     
         88 . A passive Q-switch according to  claim 86 , wherein said shells comprise lead sulfide (PbS).  
     
     
         89 . A passive Q-switch according to  claim 86 , wherein said shells comprise lead selenide sulfide (PbSe x S 1-x ).  
     
     
         90 . A passive Q-switch according to  claim 86 , wherein said shells comprise materials selected from the list consisting of: 
 materials with elements of group II-VI; and    materials with elements of group III-V.    
     
     
         91 . A passive Q-switch according to  claim 90 , wherein said materials with elements of group II-VI comprise materials selected from the list consisting of: ZnS, ZnSe, ZnTe, CdS, CdSc, CdTe, HgS, HgSe, HgTe, and MgTe.  
     
     
         92 . A passive Q-switch according to  claim 90 , wherein said materials with elements of group III-V comprise materials selected from the list consisting of: GaaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb.  
     
     
         93 . A passive Q-switch according to  claim 80 , wherein said Q-switch is operative in the cye-safe IR band ranging from 1,300 nm to 1,800 nm.  
     
     
         94 . A passive Q-switch according to  claim 93 , wherein said Q-switch is operative in the wavelength band ranging from 700 nm to 4,000 nm.  
     
     
         95 . A passive Q-switch according to  claim 80 , wherein diameter of said NCs is in the range of range of 2-18 nm.  
     
     
         96 . A passive Q-switch according to  claim 95 , wherein diameter of said NCs is in the range of 4-12 nm.  
     
     
         97 . A passive Q-switch according to  claim 80 , wherein size distribution of said NCs docs not substantially exceed 10%.  
     
     
         98 . A passive Q-switch according to  claim 80 , wherein size distribution of said NCs is less than 5%.  
     
     
         99 . A passive Q-switch according to  claim 80 , wherein shape of said NCs is selected from the list consisting of: 
 spherical; and    wire-like.    
     
     
         100 . A passive Q-switch according to  claim 80 , wherein inter-nanocrystal distance of said NCs is 0.6 nm.  
     
     
         101 . A passive Q-switch according to  claim 80 , wherein said transparent matrix is selected from the list consisting of: 
 polymer;    glass; and    sol-gel.    
     
     
         102 . A passive Q-switch according to  claim 101 , wherein said polymer matrix comprises poly-methyl-methacrylate ([—CH2C(CH3)(CO2CH3)]n (PMMA).  
     
     
         103 . A passive Q-switch according to  claim 101 , wherein said polymer matrix comprises Poly(vinyl butyral-co vinyl alcohol)n-co-vinyl-acctate (PVB).  
     
     
         104 . A passive Q-switch according to  claim 80 , wherein said transparent matrix embedded NCs are formed in a shape selected from the list consisting of: disks, rods, plates, blocks, fibers, and films.  
     
     
         105 . A passive Q-switch according to  claim 80 , wherein the concentration of the NCs in said transparent matrix is selected to provide 80-90% transmission at the desired operational wavelength.  
     
     
         106 . A passive Q-switch according to  claim 80 , wherein said transparent matrix containing said NCs is sandwiched between mediums.  
     
     
         107 . A passive Q-switch according to  claim 106 , wherein said mediums comprise two glass panes with anti-reflection coated surfaces.  
     
     
         108 . A passive Q-switch according to  claim 107  wherein anchoring of said NCs in said transparent matrix between said two glass pancs is provided by a UV cured optical adhesive.  
     
     
         109 . A passive Q-switch according to  claim 107 , wherein the parallelism the surfaces of said two glass panes is better than 20 arc seconds, and is accomplished with an autocollimator.  
     
     
         110 . A passive Q-switch according to  claim 106 , wherein said mediums comprise layer coatings.  
     
     
         111 . A passive Q-switch according to  claim 106 , wherein said mediums are transparent.  
     
     
         112 . A laser system comprising: 
 a back reflector, reflecting light;    an output coupler, reflecting light,    a pumping cavity, in which light is generated under application of an external stimulus; and    a passive Q-switch for a laser system operative at the near infrared wavelength region of 700-4,000 nm, said passive Q-switch comprising a saturable absorber comprising IV-VI semiconductor NCs embedded in a transparent matrix.    
     
     
         113 . A laser system according to  claim 112 , wherein said system is selected from the list consisting of: 
 flash-pumped;    diode-pumped; and    optical fiber based.    
     
     
         114 . A laser system according to  claim 112 , wherein said Q-switch is located between said pumping cavity and said back reflector.  
     
     
         115 . A laser system according to  claim 112 , wherein said Q-switch is located between said pumping cavity and said output coupler.  
     
     
         116 . A laser system according to  claim 112 , wherein the energy of output laser pulse of said system is 0.8-2 mJ.  
     
     
         117 . A laser system according to  claim 112 , wherein the threshold energy of said Q-switch is 5-7 J.  
     
     
         118 . New) A laser system according to  claim 112 , wherein the full width half maximum of duration of output laser pulse of said system is 20-50 ns.  
     
     
         119 . A laser system according to  claim 112 , wherein said laser rod comprises material selected from the list consisting of: 
 doped crystal;    doped glass;    gas; and    dye.    
     
     
         120 . A method for preparation of a passive Q-switch for a laser system operative at the near infrared wavelength region of 700-4,000 nm, the method comprising the procedures of: 
 fabricating IV-VI semiconductor nanocrystals (NCs) by colloidal solution technique; and    embedding said nanocrystals in a transparent matrix.    
     
     
         121 . A method according to  claim 120 , wherein said procedure of fabricating comprises fabricating lead selenide (PbSe) NCs.  
     
     
         122 . A method according to  claim 120 , wherein said procedure of fabricating comprises fabricating lead sulfide (PbS) NCs.  
     
     
         123 . A method according to  claim 120 , wherein said transparent matrix is selected from the list consisting of: 
 polymer;    glass; and    sol-gel.    
     
     
         124 . A method according to  claim 120 , further comprising the procedure of placing said transparent matrix with embedded nanocrystals between two mediums.  
     
     
         125 . A method according to  claim 124 , wherein said medium comprises a protective and non-reflective panel, board, pane, layer or coating.  
     
     
         126 . A method according to  claim 123 , wherein said polymer matrix is selected from the list consisting of: 
 poly-methyl-methacrylate (PMMA); and    poly(vinyl butyral-co vinyl alcohol)n-co-vinyl-acetate (PVB).    
     
     
         127 . A method according to  claim 120 , wherein shape of said transparent matrix is selected from the list consisting of: 
 disk;    rod;    block;    fiber;    plate; and    film.    
     
     
         128 . A method according to  claim 120 , wherein said laser system operates in at least a portion of eye-safe IR band ranging from 1,300 nm to 1,800 nm.  
     
     
         129 . A method according to  claim 120 , wherein diameter of said fabricated NCs is in the range of 2-18 nm.  
     
     
         130 . A method according to  claim 129 , wherein diameter of said fabricated NCs is in the range of 4-12 nm.  
     
     
         131 . A method according to  claim 120 , wherein size distribution of said NCs does not substantially exceed 10%.  
     
     
         132 . A method according to  claim 120 , wherein size distribution of said fabricated NCs is less than 5%.  
     
     
         133 . A method according to  claim 120 , wherein shape of said fabricated NCs is selected from the list consisting of: 
 spherical; and    wire like.    
     
     
         134 . A method according to  claim 120 , wherein inter-nanocrystal distance of said fabricated NCs is approximately 0.6 nm.  
     
     
         135 . A method according to  claim 120 , wherein said procedure of fabricating comprises fabrication of core NCs, and wherein said method further comprises the procedure of coating said core NCs with a shell having a wider energy gap than that of said core NCs.  
     
     
         136 . A method according to  claim 135 , wherein said fabrication of core NCs comprises fabricating lead selenide (PbSe) cores.  
     
     
         137 . A method according to  claim 135 , wherein said procedure of coating comprises coating said cores with lead sulfide (PbS) shells.  
     
     
         138 . A method according to  claim 135 , wherein said procedure of coating comprises coating said cores with lead selenide sulfide (PbSe x S 1-x ) shells.  
     
     
         139 . A method according to  claim 135 , wherein said procedure of coating comprises coating said cores with materials selected from the list consisting of: 
 materials with elements of group II-VI; and    materials with elements of group III-V.    
     
     
         140 . A method according to  claim 139 , wherein said procedure of coating materials with elements of group II-VI comprises applying materials selected from the list consisting of ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, Hgs, HgSe, HgTe, and MgTe.  
     
     
         141 . A method according to  claim 139 , wherein said procedure of coating materials with elements of group III-V comprises applying materials selected from the list consisting of GaN, Gap, GaAs, GaSb, InN, InP, InAs, and InSb.  
     
     
         142 . A method according to  claim 135 , comprising injecting a TOP:Se solution and a TOP:S solution into a dissolution of lead(II) acetate trihydrate in a solution of phenyl ether, oleic acid and trioctylphosphine, 
 wherein said procedure of fabricating is provided by an initial formation of PbSe cores;    wherein said procedure of coating is provided by an epitaxial cover of shells which follows; and    wherein said formation of PbSe cores is a kinetically controlled to precede said epitaxial cover of shells.    
     
     
         143 . A method according to  claim 135 , wherein said procedures of fabricating comprises the sub-procedures of: 
 dissolving lead(II) acetate trihydrate in a solution of phenyl ether, oleic acid and trioctylphosphine to form a first solution;    heating said first solution under vacuum;    heating a second solution comprising phenyl ether under vacuum;    cooling said first solution under an inert atmosphere, and further heating said second solution under an inert atmosphere;    forming a TOP:Se solution by dissolving selenium in trioctylphosphine, and further forming a TOP:S solution by dissolving sulfur in trioctylphosphine, both under inert conditions;    injecting said TOP:Se solution and said TOP:S solution into said first solution;    rapidly injecting said first solution into said second solution to form a resultant solution;    cooling said resultant solution allowing said NCs to grow;    precipitating said NCs out of said resultant solution with methanol;    separating said NCs by centrifuge; and    storing said NCs in chloroform.    
     
     
         144 . A method according to  claim 135 , wherein said procedures of fabricating comprises the sub-procedures of 
 dissolving lead(II) acetate trihydrate in a solution of phenyl ether, oleic acid and trioctylphosphine in a first receptacle;    placing phenyl ether in a second receptacle, placing said first receptacle and said second receptacle in a Schlenk line and beating them under vacuum;    cooling said first receptacle under an inert atmosphere, and further heating said second receptacle under an inert atmosphere;    forming a TOP:Se solution by dissolving selenium in trioctylphosphine, and further forming a TOP:S solution by dissolving sulfur in trioctylphosphine, both under inert conditions;    injecting said TOP:Se solution and said TOP:S solution into said first receptacle on said Schlenk line;    rapidly injecting the contents of said first receptacle into said second receptacle;    cooling said second receptacle allowing said NCs to grow;    precipitating said NCs out of second receptacle with methanol;    separating said NCs by centrifuge; and    storing said NCs in chloroform.    
     
     
         145 . An optical fiber comprising a saturable absorber comprising IV-VI semiconductor nanocrystals (NCs) embedded in a transparent matrix.  
     
     
         146 . An optical fiber according to  claim 145 , wherein said NCs comprise lead selenide (PbSe).  
     
     
         147 . An optical fiber according to  claim 145 , wherein said NCs comprise lead sulfide (PbS).  
     
     
         148 . An optical fiber according to  claim 145 , wherein said NCs have a passivated surface.  
     
     
         149 . An optical fiber according to  claim 145 , wherein said NCs are surface passivated with organic ligands.  
     
     
         150 . An optical fiber according to  claim 145 , wherein said NCs are passivated by capping of organic molecules to their surface, wherein said organic molecules are selected from the list consisting of tributylphosphine (TBP), trioctylphosphine (TOP), TOP-oxide (TOPO), oleic acid, amines, and thiols.  
     
     
         151 . An optical fiber according to  claim 145 , wherein said NCs comprise core-shell semiconductor NCs, wherein said NCs comprise cores coated by semiconductor shells having an energy band gap wider than that of the core material.  
     
     
         152 . An optical fiber according to  claim 151 , wherein said cores comprise lead selenide (PbSe).  
     
     
         153 . An optical fiber according to  claim 151 , wherein said shells comprise lead sulfide (PbS).  
     
     
         154 . An optical fiber according to  claim 151 , wherein said shells comprise lead selenide sulfide (PbSe x S 1-x ).  
     
     
         155 . An optical fiber according to  claim 151 , wherein said shells comprise materials selected from the list consisting of: 
 materials with elements of group II-VI; and    materials with elements of group II-VI.    
     
     
         156 . An optical fiber according to  claim 155 , wherein said materials with elements of group III-VI comprise materials selected from the list consisting of; ZnS, ZnSe, ZnTe, CdS, CdSe, CdTc, HgS, HgSe, HgTe, and MgTe.  
     
     
         157 . An optical fiber according to  claim 155 , wherein said materials with elements of group III-V comprise materials selected from the list consisting of: GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb.  
     
     
         158 . A fiber-optic laser system comprising: 
 an optical fiber comprising a saturable absorber comprising IV-VI semiconductor nanocrystals (NCs) embedded in a transparent matrix,