Back to results
US 5,422,907 AGranted
Pumped solid-state lasers comprising doped nanocrystal phosphors
OwnerRameshwar N. Bhargavainventor
Life of this patent
Estimating the term…
Abstract
An optically-pumped or electron-beam-pumped solid-state laser employing as the phosphor material doped nanocrystal particles which as a result of quantum confinement can be caused to exhibit discrete levels in its conduction band that can overlap with the corresponding levels in the doping activator such that resonant energy transfer of excited carriers from the conduction band of the phosphor host to that of the activator will occur. The energy levels in the activator are such as to allow very fast carrier transitions to an intermediate level and a slower radiative transition to a ground state. The result is an energy level structure similar to that of a four-level laser but capable of more efficient conversion of the pumping energy to photon generation.
Claims28
A solid-state laser comprising:
- (a) a layer of doped nanocrystal (DNC) particles doped with an activator,
- (b) said DNCs having an energy band structure with a conduction band containing first energy levels due to quantum confinement,
- (c) said activator having second atomic energy levels overlapping with the first energy levels, whereby excited carriers can transfer between said first and second energy levels, said activator also having third atomic energy levels located below in energy the second energy levels and allowing easy transition between the second and third energy levels, transitions in said activator band structure between said third energy level and a ground state being radiative and generating photons,
- (d) means for exciting carriers in the DNCs into its first energy levels allowing transfer of excited carriers to the second or third energy levels followed by their slower radiative transition to the ground state,
- (e) optical cavity means for the DNCs to enable build-up of the photon density and laser action.
2 more elements
A solid-state laser comprising:
- (a) a body of doped nanocrystals (DNC) doped with activator ions,
- (b) said DNC having an energy band structure with a conduction band containing discrete first energy levels due to quantum confinement,
- (c) said activator ions having discrete atomic second energy levels at least one of which is substantially near or at least one of the first energy levels whereby resonant energy transfer of excited carriers can occur at very high speeds between said first and second energy levels, said activator ions also having third atomic energy levels located below in energy the second energy levels and allowing easy transition of excited carriers between the second and third energy levels, carrier transitions in said activator energy levels between said third energy level and a ground state being radiative and being substantially slower than the speed of the carrier transitions from said second to said third energy levels,
- (d) means for exciting carriers in the DNC into the first energy levels whereby the resonant energy transfer of excited electrons to the second or third energy levels followed by their slower radiative transition to the ground state causes electron population inversion in the third state and a large output of photons characteristic of the carrier transition to the ground state when the carriers radiatively transit to the ground state,
- (e) optical cavity means for the DNC body to enable build-up of the photon density and laser action.
2 more elements
A solid-state laser comprising:
- (a) an optical cavity,
- (b) within the optical cavity a layer of doped nanocrystal (DNC) particles,
- (b) said DNC particles comprising a host material having an energy band structure with a conduction band with first energy levels in the conduction band,
- (c) activator elements in said host material, said activator elements having energy levels with second energy levels,
- (d) said DNC particles having a size such that said first energy levels and said second energy levels lie within approximately 1 kT of energy of each other thereby allowing a resonant energy transfer of excited electrons from the first to the second energy levels, said excited electrons in the energy levels of the activator elements undergoing transitions at a first speed to a lower level, said excited electrons in the lower level of the conduction band of the activator elements undergoing at a second speed to a ground level radiative transitions that generate photons, said first speed being at least one order of magnitude faster than the second speed whereby a population inversion of excited electrons builds up in the excited energy levels of the activator elements,
- (e) means for exciting electrons in the host material into its conduction band, whereby laser action results from the build up of photon generation within the optical cavity.
3 more elements
A solid-state laser comprising:
- (a) an optical cavity,
- (b) within the optical cavity a body of doped nanocrystal (DNC) particles,
- (b) said DNC particles comprising a host material having an energy band structure with a conduction band with first energy levels in the conduction band,
- (c) activator elements in said host material, said activator elements having split second energy levels,
- (d) said DNC particles being sized such that the first energy levels of the host are substantially at the same energy level as that of one or more of the split second energy levels in the energy level structure of the DNC whereby resonant energy transfer can occur at very high speeds between said first and second energy levels, said activator also having third energy levels located below in energy the second energy levels thereby allowing easy transition between the second and third energy levels, transitions in said activator level structure between said third energy level and a ground state being radiative and being substantially slower than the speed of the resonant energy transfer,
- (e) means for exciting electrons in the DNC into its first energy levels whereby the fast resonant energy transfer of excited electrons to the second energy levels followed by their slower radiative transition to the ground state causes electron population inversion in the third state and a large output of photons characteristic of the transition to the ground state when the electrons radiatively transit to the ground state,
- (f) optical cavity means for the DNC layer to enable build-up of the photon density and laser action.
4 more elements
Dependencies are inferred from the claim text.