1. A surface emitting laser element which emits light in a direction perpendicular to a surface of a substrate of the surface emitting laser element, comprising:
a resonator structural body including an active layer; and
first and second semiconductor distributed Bragg reflectors which sandwich the resonator structural body and include a confinement structure which can confine an injection current and a lateral mode of oscillation light at the same time by surrounding a current passing through region with an oxide containing at least an oxide formed by oxidizing a part of a layer to be selectively oxidized containing aluminum; wherein
a thickness of the layer to be selectively oxidized is at least 25 nm; and
a temperature when an oscillation threshold current becomes a minimum value is 25 \xb0 C. or less in a relationship between the temperature and the oscillation threshold current; and
wherein:
when a rectangular current pulse whose pulse period is 1 ms and whose pulse width is 500 \u03bcs is supplied to the surface emitting laser element, a relationship of (P1\u2212P2)P2\u2267\u22120.1 is satisfied when a light output after 10 ns of the pulse being supplied is defined as P1 and a light output after 1 \u03bcs of the pulse being supplied is defined as P2.
2. The surface emitting laser element as claimed in claim 1, wherein:
when a width of the current passing through region is defined as \u201cd\u201d \u03bcm, and a thickness of the oxide surrounding the current passing through region is defined as \u201ct\u201d nm, a relationship of (\u22122.54d2\u22120.14t2\u22120.998d\xb7t+53.4d+12.9t\u2212216 \u22670.9) is satisfied.
3. The surface emitting laser element as claimed in claim 1, wherein:
a part of plural semiconductor layers including the resonator structural body and the first and second semiconductor distributed Bragg reflectors has a mesa shape of a column shape or a quadrangular prism shape extending in a light emitting direction, and
the diameter of the column shape or the length of one side of the quadrangular prism shape in a cross section perpendicular to a light oscillation direction is at least 22 \u03bcm.
4. The surface emitting laser element as claimed in claim 1, wherein:
a doping concentration of an impurity in a region adjacent to the resonator structural body in the first semiconductor distributed Bragg reflector is relatively lower than the doping concentration of the impurity in other regions in the first semiconductor distributed Bragg reflector.
5. The surface emitting laser element as claimed in claim 1, wherein:
the first semiconductor distributed Bragg reflector includes plural pairs of a low refractive index layer and a high refractive index layer, and
the layer to be selectively oxidized is at a third pair or a fourth pair from the resonator structural body in the first semiconductor distributed Bragg reflector.
6. An optical scanning device which scans a surface to be scanned by light, comprising:
a light source which includes the surface emitting laser element as claimed in claim 1;
a deflector which deflects light from the light source; and
a scanning optical system which condenses light deflected by the deflector onto the surface to be scanned.
7. An image forming apparatus, comprising:
at least one image carrier; and
at least one of the optical scanning devices as claimed in claim 6 which scans light including image information onto the image carrier.
8. A surface emitting laser element which emits light in a direction perpendicular to a surface of a substrate of the surface emitting laser element, comprising:
a resonator structural body including an active layer; and
first and second semiconductor distributed Bragg reflectors which sandwich the resonator structural body and include a confinement structure which can confine an injection current and a lateral mode of oscillation light at the same time by surrounding current passing through region with an oxide containing at least an oxide formed by oxidizing a part of a layer to be selectively oxidized containing aluminum; wherein
a thickness of the layer to be selectively oxidized is at least 25 nm; and
a temperature when an oscillation threshold current becomes a minimum value is 25 \xb0 C. or less in a relationship between the temperature and the oscillation threshold current; and ps wherein:
when only a temperature of a current injection region of the resonator structural body is changed from a room temperature to 60 \xb0 C., a changing rate of a light confinement coefficient of a fundamental lateral mode in a lateral direction in the confinement structure is 10% or less.
9. A surface emitting laser element which emits light in a direction perpendicular to a surface of a substrate of the surface emitting laser element, comprising:
a resonator structural body including an active layer; and
first and second semiconductor distributed Bragg reflectors which sandwich the resonator structural body and include a confinement structure which can confine an injection current and a lateral mode of oscillation light at the same time by surrounding a current passing through region with an oxide containing at least an oxide formed by oxidizing a part of a layer to be selectively oxidized containing aluminum; wherein
a thickness of the layer to be selectively oxidized is at least 25 nm;
a maximum thickness of the oxide surrounding the current passing through region is 110 nm or less; and
a temperature when an oscillation threshold current becomes a minimum value is 25 \xb0 C. or less in a relationship between the temperature and the oscillation threshold current; and
wherein:
when a rectangular current pulse whose pulse period is 1 ms and whose pulse width is 500 \u03bcs is supplied to the surface emitting laser element, a relationship of (P1 \u2212P2)P2\u2267\u22120.1 is satisfied when a light output after 10 ns of the pulse being supplied is defined as P1 and a light output after 1 \u03bcs of the pulse being supplied is defined as P2.
10. The surface emitting laser element as claimed in claim 9, wherein:
when a width of the current passing through region is defined as \u201cd\u201d \u03bcm, and a thickness of the oxide surrounding the current passing through region is defined as \u201ct\u201d nm, a relationship of (\u22122.54d2\u22120.14t2\u22120.998d\xb7t+53.4d+12.9t\u2212216\u22670.9) is satisfied.
11. The surface emitting laser element as claimed in claim 9, wherein:
the layer to be selectively oxidized is a part of low refractive index layers of the first semiconductor distributed Bragg reflector;
the low refractive index layer including the layer to be selectively oxidized includes a first layer adjacent to the layer to be selectively oxidized and a second layer adjacent to the first layer; and
a content rate of aluminum in the first layer is lower than the content rate of aluminum in the layer to be selectively oxidized, and is higher than the content rate of aluminum in the second layer.
12. The surface emitting laser element as claimed in claim 11, wherein:
an optical thickness of the low refractive index layer including the layer to be selectively oxidized is (2n+1)\u03bb4 (n is an integer of 1 or more) when an oscillation wavelength is defined as \u03bb.
13. The surface emitting laser element as claimed in claim 11, wherein:
a difference between the content rate of aluminum in the layer to be selectively oxidized and the content rate of aluminum in the first layer is 5% or more and 20% or less.
14. The surface emitting laser element as claimed in claim 11, wherein:
a difference between the content rate of aluminum in the layer to be selectively oxidized and the content rate of aluminum in the second layer is more than 20%.
15. The surface emitting laser element as claimed in claim 9, wherein:
a gain peak wavelength in the oscillation threshold current at a room temperature is longer than a resonance wavelength in the resonator structural body.
16. An optical scanning device which scans a surface to be scanned by light, comprising:
a light source which includes the surface emitting laser element as claimed in claim 9;
a deflector which deflects light from the light source; and
a scanning optical system which condenses light deflected by the deflector onto the surface to be scanned.
17. An image forming apparatus, comprising:
at least one image carrier; and
at least one of the optical scanning devices as claimed in claim 16 which scans light including image information onto the image carrier.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An optical element for recordingreproducing a hologram, the optical element condensing a recording beam into a hologram recording medium and allowing passage of a reproduction beam from the hologram recording medium in a reverse direction with respect to the recording beam,
wherein the optical element is configured to: converge, upon incidence of a parallel beam flux as the recording beam, an on-axis beam and off-axis beams contained in the parallel beam flux onto different image points; form a beam condensing spot of the on-axis beam and the off-axis beams with a predetermined diameter at a predetermined position on an optical axis on a way to the image points; and causes at least one of the on-axis beam and the off-axis beams to have a diameter, at the predetermined position on the optical axis, smaller than the predetermined diameter of the beam condensing spot.
2. The optical element for recordingreproducing a hologram according to claim 1, wherein a diameter of one of the off-axis beams is smaller than a diameter of the on-axis beam at the predetermined position on the optical axis.
3. The optical element for recordingreproducing a hologram according to claim 1, wherein a beam flux density of one of the off-axis beams is higher than a beam flux density of the on-axis beam, at the predetermined position on the optical axis.
4. The optical element for recordingreproducing a hologram according to claim 1, wherein an image plane formed collectively by the image points is distorted curvedly or wavily in section.
5. A hologram recordingreproducing device comprising an optical element for recordingreproducing a hologram, the optical element condensing a recording beam into a hologram recording medium and allowing passage of a reproduction beam from the hologram recording medium a reverse direction from a direction of the recording beam,
wherein the optical element is one according to claim 1,
wherein, in condensing a recording beam onto the hologram recording medium by the optical element, a recording reference beam is emitted to a beam condensing spot of the recording beam for interference, and in receiving a reproduction beam from the hologram recording medium and through the optical element, a reproduction reference beam as a phase conjugate beam with regard to the recording reference beam is emitted to the hologram recording medium.