Advanced LIGO Input Optics Design Requirements Review Presentation Outline ● Design Requirements » Introduction, Production Functions (Dave R., 5 minutes) » Design Requirements (Guido*, 55 minutes) ● Conceptual Design » Introduction, Layout (David T., 10 minutes) » RF Modulation (Guido, 10 minutes) » Active Jitter Suppression (Guido, 10 minutes) » Mode Cleaner (David T., 10 minutes) » Faraday Isolation (Dave R., 10 minutes) » Mode Matching (Dave R., 10 minutes) LIGO R&D LIGO-G020229-00-D
Input Optics Product Functions ● RF modulation ● Input mode cleaning ● Additional active jitter suppression before interferometer ● Laser power control to the interferometer ● Mode matching (interferometer and mode cleaner) ● Optical isolation and distribution of sensing beams for other subsystems ● internal diagnostics LIGO R&D LIGO-G020229-00-D
IO Schematic M C Le n g t h a nd A l i g nm e nt Se nsi ng Pd s I FO C o nt r o l t o I SC I SC PSL Fa r a d a y I nt e nsi t y M C A SC I so l a t o r St a b i l i za t i o n A c t ua t i o n PSL M C M o d e M a t c hi ng St e e r i ng M o d e M a t c hi ng T e l e sc o p e M i r r o r s T e l e sc o p e C O C Po w e r A c t i ve RF C o n t r o l Ji t t e r M o d u l a t i o n M o d e Su p p r e ssi o n C l e a n e r M C Le n g t h A c t ua t i o n LIGO R&D LIGO-G020229-00-D
Not Included in IO ● Output (AS port) mode cleaner (AOS) ● Modulation drive (ISC) ● Suspension design for IO mirrors (SUS) » Suspension fabrication for large MMT ● MC length and alignment sensing and control (ISC) » should be active participation in design by IO group member ● Electronics (CDS) » MC » active jitter suppression LIGO R&D LIGO-G020229-00-D
A DVANCED LIGO Primary Requirements from Adv. LIGO Systems Design: � Frequency Noise at IFO, MC, and PSL � Intensity Noise at IFO Additional Primary Requirements calculated for � P = 125W � Sapphire mirrors � 40ppm � 50% losses on reflection � 1% difference in Arm Cavity Intensities. � DC- and RF-Sensing Include always safety factor of 10!
M ODELLING B EAM J ITTER � � 0 = TEM 00 � Input Field: ˆ 1 TEM 10 � e i ϕ 0 � 0 ϕ 0 = ω 2 π L ϕ G � Propagation: = Gouy-phase e i ( ϕ 0 + ϕ G ) ; c ; 0 p � 4 Γ 2 � 2 i Γ � � 1 = Θ 2 π w Γ � Reflection: p � 2 i Γ � 4 Γ 2 λ ; 1 � Build full IFO with these matrices � � a � Output: Dark Port Field: E out = b � Beat only TEM 00 -component a with LO (Output MC) � Repeat for Jitter SB around RF-SB. Compare with GW-Signal ) Requirements
B EAM J ITTER Beam Jitter requirement depend on Mirror Tilt: ∆Θ ITM = Θ ITM 1 � Θ ITM 2 DC-Sensing: s � 2 � 8 rad � 2 : 5 � 5 � 10 [ 2 � 10 1 ℄ a max � 10 ( f ( 5 � 10 ) = + ) ∆Θ ITM p Hz 10 f 2 RF-Sensing: s � 2 � 8 rad � 4 : 5 � 5 � 10 [ 2 � 10 1 ℄ a max � 10 ( f ( 5 : 5 � 10 ) = + ) ∆Θ ITM p Hz 10 f 2
RF-M ODULATION Two possible noise sources: � Changes in the SB-amplitude ) Change Carrier Intensity ) Creates Radiation Pressure Noise � Oscillator Phase Noise ) changes phase of LO at dark port ) scales with carrier amplitude
RF-M ODULATION Changes in SB-Amplitude DC-Sensing: � 9 10 f δ m ( f ) < p Hz [ 10 Hz ℄ m 0 RF-locking: � 9 10 f δ m ( f ) f < 100 Hz < p Hz [ 10 Hz ℄ m 0 � 8 10 δ m ( f ) f > 100 Hz < p Hz m 0
O SCILLATOR P HASE N OISE + δν � � �� = E 0 e i ω c t exp Ω t ( 2 π ft E im cos 2 π f sin ) Detuned Interferometer: Input Field: � both RF-sidebands different amplitude and phase � all noise sidebands different amplitude and phase Two contributions: � OPN-Sidebands beat with Carrier Dark Port: on PD. � Oscillator Phase Noise in LO at mixer. No Noise Cancellation anymore !
RF-M ODULATION Requirements for 180 MHz: � I SSB ( 10 Hz ) � 92 dBc/Hz < � I SSB ( 100 Hz ) � 140 dBc/Hz < � I SSB ( 1 kHz ) � 163 dBc/Hz < Critical Parameters: � Detuning in arm cavities and MI Φ φ � 7 rad � 4 rad < 10 < 10 � � � Differential Losses in arm cavities ∆ L < 15 ppm Reason: Scales with Amplitude of Carrier at DP.
S ECONDARY R EQUIREMENTS � passive suppression: mode cleaner ( 1000) Beam Jitter: � active suppression necessary Puts Requirements on Mode Cleaner: � Angular Alignment (below GW-band): Beam Jitter creates frequency noise: Θ MC � 7 rad < 10 � Angular Stability (in GW-band): MC mirror motion creates Beam Jitter: s � 2 � 8 � 2 : 5 � 12 [ 2 ℄ � 10 � 10 1 Θ i ) 2 ( f ) + ( 5 � 15 � 10 < ∆Θ ITM p Hz f 2
A DDITIONAL R EQUIREMENTS � Frequency Noise Requirement behind MC limited by radiation pressure noise � 2 Hz Hz ) 3 � 10 f < 1 kHz p Hz f � 5 Hz ) 3 � 10 f > 1 kHz p Hz � Oscillator Phase Noise and SB-Amplitude couple if FSR 6 = RF-frequency ) Difference between FSR & RF-frequency < 14Hz ) Otherwise Requirements start to change
M ODE M ATCHING Mode Matching Telescope: � Two Mirrors � Required Efficiency 95% � Adjustable to accomodate small core optics deviations Angular Requirements: � 9 rad (rms) � ∆Θ MMT < 6 � 10 p � δΘ MMT � 12 Hz < 10 =
General Design IO System Layout • Optics not in vacuum are mounted on the same table as the PSL in a clean, enclosed, and acoustically/seismically stable environment. • Conceptual Layout of IO Components on the PSL Table: RFA M M O N I TO R TO FR O M ( PERI SC O PE) VA C UU M PSL POL EOM1 EOM2 EOM2 POL WEDGE MCML VAR. ATTN A C TI VE BEA M JI TTER SU PPRESSI O N O SA LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY LIGO-G020229-00-D
Possible Methods for Minimizing Frequency Noise from Acoustic Coupling to Mirror Mounts and Periscopes • LIGO 1 suffered from coupling of acoustic noise in the PSL/IOO table environment to mirror mounts. 1) enclose PSL components in separate vacuum (with suitable vibration isolation). 2) provide low-acoustic (anechoic) enclosure around PSL with all noise producing devices (fans, etc) outside this enclosure. • PSL/IOO table of L1 was not stiff enough to constrain the (heavy) periscope frame first employed; eventually a lighter design was used. 1) move periscope into vacuum system (requires a HAM viewport at table level). 2) raise table to eliminate periscope. • Both treatments are outside the scope of the IOO subsystem alone. LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY LIGO-G020229-00-D
In-vacuum optics • With the exception of the Faraday isolator, all main IFO beam optics including and following the mode cleaner will be suspended. • Diagnostic beam optics for IFO and MC control will be located on fixed mounts. • Output ports in the HAMs used as optical feedthroughs for sensing beams. LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY LIGO-G020229-00-D
LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY LIGO-G020229-00-D
LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY LIGO-G020229-00-D
LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY LIGO-G020229-00-D
Dimensional Constraints • IO system located on PSL table. HAMs 1, 2, and 3. HAM 3 also holds the power recycling mirror. • Dimensions: Item Unit Value 16 x 5 PSL table area dimensions ft x ft HAM1(7) - HAM2(8) spacing (center-center) m 13.72 HAM2(8) - HAM3(9) spacing (center-center) m 2.63 m x m 1.90 x 1.70 HAM1(7) stack area dimensions (L x W) (TBR) m x m 1.90 x 1.70 HAM2(8) stack area dimensions (L x W) (TBR) m x m 1.90 x 1.70 HAM3(9) stack area dimensions (L x W) (TBR) HAM1,2 (7,8) Connecting Beam Tube Diameter m 1.2* * HAM1,2 and HAM 7,8 beam tube to be replaced LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY LIGO-G020229-00-D
Dimensional Constraints, cont. ∆ z (HAM1-HAM2, local coordinates, LHO) 8.49 † mm ∆ z (HAM2-HAM3, local coordinates, LHO) 1.59 † mm ∆ z (HAM7-HAM8, local coordinates, LHO) -8.49 † mm ∆ z (HAM8-HAM9, local coordinates, LHO) -1.59 † mm ∆ z (HAM1-HAM2, local coordinates, LLO) 4.28 † mm ∆ z (HAM2-HAM3, local coordinates, LLO) 0.80 † mm † The LHO x -axis slopes downward by 0.619 mrad; the y -axis slopes upward by 0.012 mrad. WHAM1 (7) is 8.5 mm higher (lower) than WHAM2 (8). At LLO the x- axis slopes downward by 0.312 mrad and the y- axis slopes downward by 0.612 mrad. LHAM1 is 4.3 mm higher than LHAM2. • Suspensions must either be raised on platform or have adjustment capability so that the plane of the MC beam is level • Capability for optical levers on all suspended mirrors required. LASER INTERFEROMETER GRAVITATIONAL WAVE OBSERVATORY LIGO-G020229-00-D
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