Diffractive MEMS device

• US 10,394,015 B2
• Filed: 03/27/2017
• Issued: 08/27/2019
• Est. Priority Date: 01/11/2012
• Status: Active Grant

• Current Assignee: Lumentum Operations, LLC (Lumentum Holdings Inc.)
• Original Assignee: Lumentum Operations, LLC (Lumentum Holdings Inc.)
• Inventors: Miller, John Michael, Jin, Wenlin
• Primary Examiner(s): Deherrera, Kristina M
• Application Number:
  US15/470,423
• Publication Number:
  US 20170199374A1
• Time in Patent Office: 883 Days
• Field of Search: 359558-576, 3591961-2263, 216 2
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 5/18 Diffraction gratings holographic optical elements G02B5/32, G03H; integrally combined with optical fibres G02B6/02057; for coupling light guides G02B6/34; integrally combined with optical integrated light guides G02B6/12; grating systems G02B27/44
• CPC Class Codes: G02B 5/1861 Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: H01S 5/06 Arrangements for controlling the laser output parameters, e.g. by operating on the active medium

Abstract

A diffractive MEMS device has an in-plane binary reflective diffraction pattern formed in an outer surface of a tillable platform. The binary reflective diffraction pattern includes rectangular or trapezoidal ridges and valleys, or grooves, of a same depth. The binary reflective diffractive pattern has a high diffraction efficiency even though the surfaces of the “grooves” or “ridges” are not perpendicular to the incoming optical beam. The diffractive pattern is supported by a pair of torsional hinges and is tiltable by an electrostatic actuator. The electrostatic actuator can include at least one side electrode for linearization of dependence of tilt angle on the voltage applied to the actuator.

Claims

1. A device comprising:

a substrate;

a platform supported over the substrate and tiltable about a first axis; and

an electrostatic actuator comprising a stator and a rotor for tilting the platform about the first axis when a first control voltage is applied between the stator and the rotor, wherein

the stator and the rotor are located above the substrate,

a slope generated by the stator and the rotor increases with a tilt angle of the platform,

a first stator side electrode extends upwardly from the substrate for an electrostatic interaction with the platform, and

a slope generated by the first stator side electrode decreases with the tilt angle of the platform, thereby providing for a linear dependence of a control voltage on the tilt angle.

2. The device of claim 1, wherein the platform comprises a binary diffractive surface relief pattern, comprising a binary diffraction grating, and a conforming reflective metal layer disposed over the binary diffractive surface relief pattern.

3. The device of claim 2, wherein

the binary diffractive surface relief pattern comprises ridges comprising sidewalls and separated by trenches, and

the ridges have rectangular or trapezoidal cross-sections.

4. The device of claim 3, wherein the conforming reflective metal layer is disposed on the sidewalls of the ridges and in the trenches.

5. The device of claim 1, wherein the first stator side electrode extends to at least 50% to 150% of a distance between the substrate and the platform when no voltage is applied between the stator and the rotor.

6. The device of claim 1, wherein the platform further includes a flange that surrounds at least some of the first stator side electrode.

7. The device of claim 1, wherein

the stator further comprises a first stator comb extending from the substrate towards the platform,

the rotor comprises a first rotor comb extending from the platform towards the substrate, and

the first rotor comb is interdigitated with the first stator comb.

8. The device of claim 7, wherein

the stator further comprises a second stator comb extending from the substrate towards the platform,

the rotor further comprises a second rotor comb extending from the platform towards the substrate, and

the second rotor comb is interdigitated with the second stator comb.

9. The device of claim 1, further comprising:

a second stator side electrode extending upwardly from the substrate for an electrostatic interaction with the platform.

10. The device of claim 9, wherein the second stator side electrode extends to at least 50% to 150% of a distance between the substrate and the platform when no voltage is applied between the stator and the rotor.

11. The device of claim 9, wherein the platform comprises first and second flanges extending laterally therefrom and surrounding the first stator side electrode and the second stator side electrode, respectively.

12. The device of claim 9, further comprising:

a third stator side electrode and a fourth stator side electrode, each extending from the substrate on opposite sides of the platform, for an electrostatic interaction with the platform, such that a first flange is at least partially disposed between the first stator side electrode and the third stator side electrode and a second flange is at least partially disposed between the second stator side electrode and the fourth stator side electrode.

13. The device of claim 12, further comprising:

a fifth stator side electrode and a sixth stator side electrode, each extending from the substrate on opposite sides of the platform, for an electrostatic interaction with the platform.

14. The device of claim 13, wherein the fifth stator side electrode and the sixth stator side electrode each extend to at least 50% to 150% of a distance between the substrate and the platform when no voltage is applied between the stator and the rotor.

15. The device of claim 13, wherein the platform further comprises third and fourth flanges extending laterally therefrom and surrounding the fifth stator side electrode and the sixth stator side electrode, respectively.

16. The device of claim 15, further comprising:

a seventh stator side electrode and an eighth stator side electrode, each extending from the substrate on opposite sides of the platform, for an electrostatic interaction with the platform, such that the third flange is at least partially disposed between the fifth stator side electrode and the seventh stator side electrode and the fourth flange is at least partially disposed between the sixth stator side electrode and the eighth stator side electrode.

17. A tunable semiconductor laser comprising:

a semiconductor chip for providing optical gain at a lasing wavelength; and

the device of claim 1, optically coupled to the semiconductor chip, for providing a wavelength selective optical feedback for tuning the lasing wavelength.

18. The tunable semiconductor laser of claim 17, wherein a pitch parameter is between 75% and 125% of the lasing wavelength.

19. The tunable semiconductor laser of claim 17, wherein the semiconductor chip includes a Mach Zehnder modulator, a semiconductor optical amplifier, a grating, a laser gain section, and a phase section.

20. The tunable semiconductor laser of claim 17, wherein the semiconductor chip includes two facets and each facet is coated with an anti-reflection coating and a translucent coating.