Nonlinear optical switch

• US 6,760,492 B1
• Filed: 06/18/2002
• Issued: 07/06/2004
• Est. Priority Date: 06/19/2001
• Status: Expired due to Fees

• Current Assignee: Hossam Zoweil, John Lit
• Original Assignee: Hossam Zoweil, John Lit
• Inventors: Lit, John, Zoweil, Hossam
• Primary Examiner(s): Le, Thien M.
• Assistant Examiner(s): TRAIL, ALLYSON NEEL
• Application Number:
  US10/173,435
• Time in Patent Office: 749 Days
• Field of Search: 385/5, 385/37, 385/16, 385/18, 385/24
• US Class Current: 385/5
• CPC Class Codes: G02F 1/3511 Self-focusing or self-trapping of light; Light-induced birefringence; Induced optical Kerr-effect
• CPC Class Codes: G02F 1/3515 All-optical modulation, gating, switching, e.g. control of a light beam by another light beam G02F1/353, G02F1/37, G02F1/39 take precedence
• CPC Class Codes: G02F 2201/307 Reflective grating, i.e. Bragg grating
• CPC Class Codes: G02F 2203/05 wavelength dependent

Abstract

The invention provides an optical switch for operation by an incident light. The optical switch has a linear grating portion having an average linear refractive index and a nonlinear grating portion, meeting at an interface. The nonlinear grating portion includes a plurality of periodically alternating layers of nonlinear materials having different refractive indices. The linear grating portion and the nonlinear grating portion are positioned to form a continuous sequence of alternating high and low refractive indices at low intensities. The incident light is substantially reflected at low intensities. At high intensities, a continuous sequence of alternating high and low refractive indices is formed, interrupted by a discontinuity at the interface, and the nonlinear grating portion has a second average nonlinear refractive index which is substantially equivalent to the average linear refractive index. Light having a narrow band of frequencies is substantially transmitted at high intensities.

Claims

1. An optical switch for operation by an incident light, the optical switch having:

(a) a nonlinear grating portion including a plurality of periodically alternating layers of a negative nonlinear material having a first nonlinear refractive index and a positive nonlinear material having a second nonlinear refractive index when the incident light has a first intensity, the first nonlinear refractive index being higher than the second nonlinear refractive index, the nonlinear grating portion having a first average nonlinear refractive index when the incident light has the first intensity, the periodically alternating layers forming a first nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices when the incident light has the first intensity, and the nonlinear grating portion having a nonlinear grating period;

(b) a linear grating portion positioned adjacent to the nonlinear grating portion, the linear grating portion and the nonlinear grating portion meeting at an interface, the linear grating portion including a plurality of periodically alternating layers of a first linear material having a first linear refractive index and a second linear material having a second linear refractive index, the first linear refractive index being higher than the second linear refractive index, the periodically alternating layers comprising the linear grating portion forming a linear grating portion sequence of alternating relatively higher and relatively lower refractive indices, the linear grating portion having an average linear refractive index substantially equivalent to the first average nonlinear refractive index, and the linear grating portion having a linear grating portion period substantially equivalent to the nonlinear grating portion period;

(c) the nonlinear grating portion and the linear grating portion being positioned relative to each other such that the first nonlinear grating portion sequence and the linear grating portion sequence form a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, and the incident light having the first intensity is substantially reflected;

(d) the negative nonlinear material having a third nonlinear refractive index and the positive nonlinear material having a fourth nonlinear refractive index when the incident light has a second intensity, the second intensity being substantially higher than the first intensity, and the fourth nonlinear refractive index being substantially higher than the third nonlinear refractive index, such that the periodically alternating layers comprising the nonlinear grating portion form a second nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices when the incident light has the second intensity; and

(e) the second nonlinear grating portion sequence and the linear grating portion sequence forming a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by a discontinuity at the interface of the linear grating portion and the nonlinear grating portion, such that, when the incident light has the second intensity, the nonlinear grating portion has a second average nonlinear refractive index which is substantially equivalent to the average linear refractive index, and light having a narrow band of frequencies is substantially transmitted,

whereby, when the incident light has the first intensity, the incident light is substantially reflected by the optical switch, and when the incident light has the second intensity, light having a narrow band of frequencies is substantially transmitted by the optical switch.

7. An optical switch as defined in any of claims 1-6 additionally including a gain medium for amplifying the incident light and a means for exciting the gain medium, such that when the incident light is supplied to the gain medium and the gain medium is excited, the gain medium amplifies the incident light.

2. An optical switch for operation by an incident light, the optical switch having:

(a) a nonlinear grating portion including a plurality of periodically alternating layers of a negative nonlinear material having a first nonlinear refractive index and a positive nonlinear material having a second nonlinear refractive index when the incident light has a first intensity, the first nonlinear refractive index being higher than the second nonlinear refractive index, the nonlinear grating portion having a first average nonlinear refractive index when the incident light has the first intensity, the periodically alternating layers forming a first nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices, and the nonlinear grating portion having a nonlinear grating portion period;

(b) a linear grating portion including a plurality of periodically alternating layers of a first linear material having a first linear refractive index and a second linear material having a second linear refractive index, the first linear refractive index being higher than the second linear refractive index, the periodically alternating layers comprising the linear grating portion forming a linear grating portion sequence of alternating relatively higher and relatively lower refractive indices, and the linear grating portion having an average linear refractive index, the linear grating portion having a linear grating portion period substantially equivalent to the nonlinear grating portion period;

(c) a phase shift portion disposed between the nonlinear grating portion and the linear grating portion;

(d) the nonlinear grating portion and the linear grating portion being positioned relative to each other such that the first nonlinear grating portion sequence and the linear grating portion sequence form a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by a first discontinuity at the phase shift portion;

(e) the first average nonlinear refractive index being substantially equivalent to the average linear refractive index, such that when incident light has the first intensity, light having a first narrow band of frequencies is transmitted;

(f) the negative nonlinear material having a third nonlinear refractive index and the positive nonlinear material having a fourth nonlinear refractive index when the incident light has a second intensity, the second intensity being substantially higher than the first intensity, and the fourth nonlinear refractive index being substantially higher than the third nonlinear refractive index, such that the periodically alternating layers comprising the nonlinear grating portion form a second nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices when the incident light has the second intensity; and

(g) the second nonlinear grating portion sequence and the linear grating portion sequence forming a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by a second discontinuity at the phase shift portion, the second discontinuity differing substantially from the first discontinuity, such that, when the incident light has the second intensity, the nonlinear grating portion has a second average nonlinear refractive index which is substantially equivalent to the average linear refractive index, and light having at least one second narrow band of frequencies is transmitted by the optical switch,

whereby, when the incident light has the first intensity, light having the first narrow band of frequencies is substantially transmitted by the optical switch, and when the incident light has the second intensity, light having the second narrow band of frequencies is substantially transmitted by the optical switch.

3. An optical switch for operation by an incident light, the optical switch having:

(a) a nonlinear grating portion including a plurality of periodically alternating layers of a first negative nonlinear material having a first nonlinear refractive index and a second negative nonlinear material having a second nonlinear refractive index when the incident light has a first intensity, the first nonlinear refractive index being higher than the second nonlinear refractive index, the nonlinear grating portion having a first average nonlinear refractive index when the incident light has the first intensity, the periodically alternating layers forming a first nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices, and the nonlinear grating portion having a nonlinear grating portion period;

(b) a linear grating portion including a plurality of periodically alternating layers of a first linear material having a first linear refractive index and a second linear material having a second linear refractive index, the first linear refractive index being higher than the second linear refractive index, the periodically alternating layers comprising the linear grating portion forming a linear grating portion sequence of alternating relatively higher and relatively lower refractive indices, and the linear grating portion having an average linear refractive index, the linear grating portion having a linear grating portion period substantially equivalent to the nonlinear grating portion period;

(c) a phase shift portion disposed between the nonlinear grating portion and the linear grating portion;

(d) the nonlinear grating portion and the linear grating portion being positioned relative to each other such that the first nonlinear grating portion sequence and the linear grating portion sequence form a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by a discontinuity at the phase shift portion;

(e) the first average nonlinear refractive index differing substantially from the average linear refractive index when the incident light has the first intensity, such that incident light having the first intensity is substantially reflected;

(f) the first negative nonlinear material having a third nonlinear refractive index and the second negative nonlinear material having a fourth nonlinear refractive index when the incident light has a second intensity, the second intensity being substantially higher than the first intensity, and the fourth nonlinear refractive index being substantially higher than the third nonlinear refractive index, such that the periodically alternating layers comprising the nonlinear grating portion form a second nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices when the incident light has the second intensity; and

(g) the second nonlinear grating portion sequence and the linear grating portion sequence forming a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by the discontinuity at the phase shift portion, such that, when the incident light has the second intensity, the nonlinear grating portion has a second average nonlinear refractive index which is substantially equivalent to the average linear refractive index, and light having at least one narrow band of frequencies is substantially transmitted,

whereby, when the incident light has the first intensity, the incident light is substantially reflected by the optical switch, and when the incident light has the second intensity, light having at least one narrow band of frequencies is substantially transmitted by the optical switch.

4. An optical switch for operation by an incident light, the optical switch having:

(a) a nonlinear grating portion including a plurality of periodically alternating layers of a first positive nonlinear material having a first nonlinear refractive index and a second positive nonlinear material having a second nonlinear refractive index when the incident light has a first intensity, the first nonlinear refractive index being higher than the second nonlinear refractive index, the nonlinear grating portion having a first average nonlinear refractive index when the incident light has the first intensity, the periodically alternating layers forming a first nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices, and the nonlinear grating portion having a nonlinear grating portion period;

(b) a linear grating portion including a plurality of periodically alternating layers of a first linear material having a first linear refractive index and a second linear material having a second linear refractive index, the first linear refractive index being higher than the second linear refractive index, the periodically alternating layers comprising the linear grating portion forming a linear grating portion sequence of alternating relatively higher and relatively lower refractive indices, and the linear grating portion having an average linear refractive index, the linear grating portion having a linear grating portion period substantially equivalent to the nonlinear grating portion period;

(c) a phase shift portion disposed between the nonlinear grating portion and the linear grating portion;

(d) the nonlinear grating portion and the linear grating portion being positioned relative to each other such that the first nonlinear grating portion sequence and the linear grating portion sequence form a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by a discontinuity at the phase shift portion;

(e) the nonlinear grating portion having a first average nonlinear refractive index differing substantially from the average linear refractive index when the incident light has the first intensity, such that incident light having the first intensity is substantially reflected by the optical switch;

(f) the first positive nonlinear material having a third nonlinear refractive index and the second positive nonlinear material having a fourth nonlinear refractive index when the incident light has a second intensity, the second intensity being substantially higher than the first intensity, and the fourth nonlinear refractive index being substantially higher than the third nonlinear refractive index, such that the periodically alternating layers comprising the nonlinear grating portion form a second nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices when the incident light has the second intensity; and

(g) the second nonlinear grating portion sequence and the linear grating portion sequence forming a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by the discontinuity at the phase shift portion, such that, when the incident light has the second intensity, the nonlinear grating portion has a second average nonlinear refractive index which is substantially equivalent to the average linear refractive index, and light having at least one narrow band of frequencies is transmitted,

whereby, when the incident light has the first intensity, the incident light is substantially reflected by the optical switch, and when the incident light has the second intensity, light having at least one narrow band of frequencies is substantially transmitted by the optical switch.

5. An optical switch for operation by an incident light, the optical switch having:

(a) a nonlinear grating portion including a plurality of periodically alternating layers of a first positive nonlinear material having a first nonlinear refractive index and a second positive nonlinear material having a second nonlinear refractive index when the incident light has a first intensity, the first nonlinear refractive index being higher than the second nonlinear refractive index, the nonlinear grating portion having a first average nonlinear refractive index n₁ when the incident light has the first intensity, the periodically alternating layers forming a first nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices, and the nonlinear grating portion having a nonlinear grating portion period P₂;

(b) a linear grating portion including a plurality of periodically alternating layers of a first linear material having a first linear refractive index and a second linear material having a second linear refractive index, the first linear refractive index being higher than the second linear refractive index, the periodically alternating layers comprising the linear grating portion forming a linear grating portion sequence of alternating relatively higher and relatively lower refractive indices, and the linear grating portion having an average linear refractive index n₀, the linear grating portion having a linear grating portion period P₁ substantially greater than the nonlinear grating portion period P₂;

(c) a phase shift portion disposed between the nonlinear grating portion and the linear grating portion;

(d) the nonlinear grating portion and the linear grating portion being positioned relative to each other such that the first nonlinear grating portion sequence and the linear grating portion sequence form a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by a discontinuity at the phase shift portion;

(e) the first positive nonlinear material having a third nonlinear refractive index and the second positive nonlinear material having a fourth nonlinear refractive index when the incident light has a second intensity, the second intensity being substantially higher than the first intensity, and the fourth nonlinear refractive index being substantially higher than the third nonlinear refractive index, such that the periodically alternating layers comprising the nonlinear grating portion form a second nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices when the incident light has the second intensity;

(f) the second nonlinear grating portion sequence and the linear grating portion sequence forming a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by the discontinuity at the phase shift portion;

(g) the nonlinear grating portion having a second average nonlinear grating refractive index n₂ when the incident light has the second intensity, such that the following equation;

6. An optical switch for operation by an incident light, the optical switch having:

(a) a nonlinear grating portion including a plurality of periodically alternating layers of a first negative nonlinear material having a first nonlinear refractive index and a second negative nonlinear material having a second nonlinear refractive index when the incident light has a first intensity, the first nonlinear refractive index being higher than the second nonlinear refractive index, the nonlinear grating portion having a first average refractive index n₁ when the incident light has the first intensity, the periodically alternating layers forming a fist nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices, and the nonlinear grating portion having a nonlinear grating portion period P₂;

(b) a linear grating portion including a plurality of periodically alternating layers of a first linear material having a first linear refractive index and a second linear material having a second linear refractive index, the first linear refractive index being higher than the second linear refractive index, the periodically alternating layers comprising the linear grating portion forming a linear grating portion sequence of alternating relatively higher and relatively lower refractive indices, and the linear grating portion having an average linear refractive index n₀, the linear grating portion having a linear grating portion period P₁ substantially less than the nonlinear grating portion period P₂;

(c) a phase shift portion disposed between the nonlinear grating portion and the linear grating portion;

(d) the nonlinear grating portion and the linear grating portion being positioned relative to each other such that the first nonlinear grating portion sequence and the linear grating portion sequence form a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by a discontinuity at the phase shift portion;

(e) the first negative nonlinear material having a third nonlinear refractive index and the second negative nonlinear material having a fourth nonlinear refractive index when the incident light has a second intensity, the second intensity being substantially higher than the first intensity, and the fourth nonlinear refractive index being substantially higher than the third nonlinear refractive index, such that the periodically alternating layers comprising the nonlinear grating portion form a second nonlinear grating portion sequence of alternating relatively higher and relatively lower refractive indices when the incident light has the second intensity;

(f) the second nonlinear grating portion sequence and the linear grating portion sequence forming a continuous sequence of alternating relatively higher and relatively lower refractive indices along the optical switch, interrupted by the discontinuity of the phase shift portion;

(g) the nonlinear grating portion having a second average nonlinear refractive index n₂ when the incident light has the second intensity, such that the following equation;