Bolometer Group

Ultimate Cold-Electron Bolometer

with Strong Electrothermal Feedback

Leonid Kuzmin

Chalmers University of TechnologyBolometer GroupBolometer Group

Björkliden - 2004

Through the thorns to the stars!

Igenom törnen mot stjärnorna!

Через тернии к звездам!

OutlineOutline

Cold-Electron Bolometer (CEB) Comparison with TESNEP with background loadGeneral Ultimate NEP formulaExperimentsPossible developmentsConclusions

Noise Equivalent power less than 10-20 W/Hz1/2 !?

Wavelengths: submillimeter/infrared bands: 40-500 m.

100x100 pixel detector arrays !?

Readout electronics with multiplexing (SQUID?)

Ideal detector: counting individual photons and providing some energy discrimination !?

Detector requrements Detector requrements for future space telescopesfor future space telescopes

SPIRIT, SPECS, …SPIRIT, SPECS, …

Cold-Electron Bolometer (CEB) Cold-Electron Bolometer (CEB) withwith Capacitive Coupling and Capacitive Coupling and Thermal Isolation by Tunnel JunctionsThermal Isolation by Tunnel Junctions

Current responsivity:  

CEB with Electrothermal Feedback (ETF)CEB with Electrothermal Feedback (ETF)

[ ],1)1(

//

ωτω iL

L

G

TI

CiGG

TI

P

IS

coolphecooli ++

∂∂=

++

∂∂=

∂

∂=

Λ−

- effective time constant  ( ~10 ns)

1>>= −phecool GGL - ETF gain

)1(0 += Lττ

- e-ph time constant (~ 10 s at 100 mK)pheGC −Λ=0τ

CEB. Cooling Thermal ConductanceCEB. Cooling Thermal Conductance

P0= 0

Tph

P0=0.1 pW

Te

0

2

4

6

8

10

12

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Temperature(K)

Te

Output PowerOutput Power

0

0.5

1

1.5

0 0.5 1 1.5

Pcool z Ps

Outputpower

Pe-ph

Ps = Pcool + Pe-ph

Outputpower

Pbias0

Saturation Power Psat = 1 pW

Saturation Power Psat > 100 pW

(corresponds to Tc=1.2 K)

Signal Power, Ps (pW)

TES

CEB

Ptot=Pbias+Ps

-Pbiasz Ps

TES and CEB. Operating TemperatureTES and CEB. Operating Temperature

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.5 1 1.5

Signal Power, P (pW)

TES - "Tc -detector"

CEB - "0 -detector"

NEPe-ph

2 = 4kTe

2G

Tbath

dc bias heating

cooling

Tc

Turning Point from ”Heating” to ”CoolingTurning Point from ”Heating” to ”Cooling

Te could be decreased bydirect electron cooling (!) :

P0 - removed by SIN junctions

Te cool << Te = 230 mK

P0

Tph

Te100 mK 230 mK

time

Pbias - heating!

P0

TphTe100 mK 230 mK

time

Transition Edge Sensor (TES)

Te should be even more increased bydc bias heating (!) :

Ptotal = P0 +Pbias , Pbias = Pmax signalTe heat > Te = 230 mK

0 0

? ?Te heat

Te cool

Electron-Phonon NoiseElectron-Phonon NoiseEquilibrium case:  

 NEPe-ph2 = 4 kBT2 Ge-ph = 20 kBV T6

V- volume

 Nonequilibrium case: (Jochum et al. – 1998)

NEPe-ph2 = 10 kBV (Tph

6 + Te6)

Direct electron cooling

Te = (Tph5 + P

V)1/5

SIN junction noiseSIN junction noise

For strong electron cooling: Pcool >> Pe-ph  

NEPshot = ( 2 P0 kB Te )1/2

P0 – background power load

For P0 = 0.1 pW, Te = 50 mK, NEPshot = 4*10 –19 W/Hz1/2

22

22 2 ω

ωωω δδδδ PS

IPSINEP

IISIN +−=

Shot noise Correlation term Heat flow noise

General Ultimate NEP FormulaGeneral Ultimate NEP Formula

NEPshot = ( 2 P0 Equant )1/2

P0 – background power load

Equant – energy level of P0 quantization

Equant = kB Te - normal metal absorber

Equant = - superconducting absorber

Kuzmin, Madrid - 2003General NEPshot - dominates

NEP e-ph.NEP e-ph. Normal metalNormal metal and and SuperconductingSuperconducting absorbers absorbers

Limit NEP for different bolometersLimit NEP for different bolometers

NEPshot = ( 2 P0 Equant )1/2

CEB: P0 = 10 fW, Te = 50 mK,

NEPshot = 1*10 –19 W/Hz1/2

TES: P0 = 10 fW, Te = 500 mK,

NEPshot = 4*10 –19 W/Hz1/2

Kinetic Ind. Det: P0 = 10 fW, = 2 K (Al,

00eV) NEPshot = 7*10 –19 W/Hz1/2

General Limit NEP formulaGeneral Limit NEP formulaSystems with linear on T thermal conductance- Spider-web TES with conductance through the legs- CEB with cooling through SIN tunnel junctions (weak dependence on T: G ~T1/2), …

NEPshot = 2 P0 Equant

Systems with dominant e-ph thermal conductance (strong nonlinearity on T: Ge-ph ~T4 )

- all bolometers on plane substrates with e-ph conductance- antenna-coupled TES on chip, - NHEB with Andreev mirrors …

NEPshot e-ph = 10 P0 Equant

Electron Cooling and NEP measurementsElectron Cooling and NEP measurements I. Agulo, L. Kuzmin and M. TarasovI. Agulo, L. Kuzmin and M. Tarasov

Strip width0m

Attowatt NEP in dc experimentsAttowatt NEP in dc experiments

Both, Quasiparticle multiplier, 1987 Both et al., Quasiparticle transistor, 1999

Cascade Quasiparticle Amplifier Cascade Quasiparticle Amplifier and CEBand CEB

A

Conclusions:Conclusions:We propose the

-- simplest-- smallest (< 2 m) -- coldest (Te < Tph) -- fastest(~ 10 ns) --- most sensitive (under real background Po) -- not saturated (up to Tc of electrodes, >100 pW)-- ideal ”0-detector” (could not be better!) -- easy multiplied on plane substrate (for large arrays)-- easy amplified by Cascade Quasiparticle Amplifier-- easy multiplexed by SQUIDs-- easy fit in any experiment (from submm to near-IR)

Cold-Electron Bolometer with Strong Electrothermal Feedback