Substrate transferred monocrystalline bragg mirrors
A mirror assembly comprising a carrier substrate; a stack comprising a plurality of alternating monocrystalline semiconductor layers of a first and a second type, wherein the layers of the first type have an index of refraction higher than the layers of the second type thereby forming a Bragg mirror; wherein the carrier substrate is curved having a radius of curvature between 0.1 m and 10 km; wherein the stack is attached to the curved carrier substrate.
1. A low absorption crystalline mirror assembly comprising:
a curved carrier substrate; and
a crystalline stack comprising a plurality of alternating single-crystal semiconductor layers of a first and a second type, wherein the layers of the first type have an index of refraction higher than the layers of the second type, thereby forming a Bragg mirror; wherein the carrier substrate is curved having a radius of curvature (ROC) between 0.1 m and 10 m or between 1 km and 10 km, wherein the crystalline stack being attached to the curved carrier substrate, wherein the crystalline stack is configured to have a limiting loss angle of between 10 −5 and 10 −6 and the crystalline stack is adapted to have a low thermo-mechanical and/or Brownian noise and the crystalline stack has a total thickness of 6-10 μm,
wherein the single-crystal semiconductor layers of the mirror comprise monocrystalline epitaxial layers based on an AlGaAs ternary alloy, wherein the semiconductor layer of the first and second type comprise alternating Al x Ga 1-x As/Al y Ga 1-y , 0<x<1, 0<y<1, with x<0.5 and y>0.5.
2. The mirror assembly according to claim 1 , wherein the carrier substrate is transparent, in particular at a wavelength of 1064 nm or 1550 nm, and wherein the surface of the carrier substrate is polished.
3. The mirror assembly according to claim 1 , wherein the carrier substrate comprises Si0 2 , Si, Sapphire, or ultra-low expansion (ULE) glass.
4. The mirror assembly according to claim 1 , wherein the crystalline stack is attached to the carrier substrate by at least one of van der Waals forces bonding or covalent bonding.
5. An optical resonator for optical precision measurements comprising two mirror assemblies according to claim 1 , the reflecting surfaces of the mirrors facing each other at a predetermined distance, wherein for a ROC of 0.1 m to 10 m, a spacer having a predetermined thickness is interposed between the two mirrors assemblies, wherein the spacer provides the predetermined distance between the two mirrors.
6. An optical resonator for optical precision measurements comprising two mirror assemblies according to claim 1 , the reflecting surfaces of the mirrors facing each other at a predetermined distance, wherein for a ROC of 1 km to 10 km, each mirror assembly is individually supported.
7. The mirror assembly according to claim 1 having a reflexivity of larger than 99.99% at a center wavelength of between 600 nm-3 μm.
8. A method for manufacturing a low absorption crystalline mirror assembly, the mirror assembly comprising a curved carrier substrate, and a crystalline stack comprising a plurality of alternating single-crystal semiconductor layers of a first type and a second type, wherein the layers of the first type have an index of refraction higher than an index of refraction of the layers of the second type; wherein the carrier substrate is curved, having a radius of curvature (ROC) between 0.1 m and 10 m or between 1 km and 10 km; the method comprising the steps of:
providing a first substrate;
providing the curved carrier substrate;
epitaxially forming on the first substrate the crystalline stack of alternating single-crystal semiconductor layers of the first type and the second type, thereby forming a Bragg mirror;
detaching the stack from the first substrate; and
after detaching the stack from the first substrate, attaching the stack to the curved carrier substrate,
wherein the crystalline stack is configured to have a limiting loss angle of between 10 −5 and 10 −6 and the crystalline stack is adapted to have a low thermo-mechanical and/or Brownian noise, and
wherein the single-crystal semiconductor layers of the mirror are monocrystalline epitaxial layers based on an AlGaAs ternary alloy, wherein the semiconductor layer of the first and second type are formed of alternating Al x Ga 1-x As/Al y Ga 1-y As, 0<x<1, 0<y<1, with x<0.5 and y>0.5.
9. The method according to claim 8 , wherein the first substrate comprises GaAs or Ge.
10. The method according to claim 8 , wherein the carrier substrate is transparent, in particular at a wavelength of 1064 nm or 1550 nm, and wherein the surface of the carrier substrate is polished.
11. The method according to claim 8 , wherein the carrier substrate comprises SiO 2 , Si, Sapphire, or ultra-low expansion (ULE) glass.
12. The method according to claim 8 , wherein the crystalline stack is detached from the first substrate by using chemo-mechanical substrate removal or epitaxial lift-off processes.
13. The method according to claim 8 ; wherein the stack is attached to the carrier substrate by at least one of van der Waals forces bonding and covalent bonding.
14. The method according to claim 13 , wherein the stack is bonded to the carrier substrate and wherein the bond is strengthened by annealing.
15. The method according to claim 8 , wherein epitaxially forming the crystalline stack of alternating single-crystal semiconductor layers of the first type and the second type includes performing molecular beam epitaxy (MBE).
16. The method according to claim 8 , wherein epitaxially forming the crystalline stack of alternating single-crystal semiconductor layers of the first type and the second type includes performing metalorganic vapor phase epitaxy (MOVPE).
17. The method according to claim 8 wherein the mirror assembly has a reflectivity of larger than 99.99% at a center wavelength of between 600 nm-3 μm.
18. A low absorption crystalline mirror assembly manufactured according to the method of claim 8 .