Hobbs Electro Optics QL01 Series Manual de usuario
QL01 Series
Quantum-Limited Photoreceivers
User’s Guide And Reference
Rev. 1.22
QL01 Series
Quantum-Limited Photoreceivers
Rev. 1.22
Philip C. D. Hobbs
Hobbs ElectroOptics/ElectroOptical Innovations, LLC.
i
LEGAL NOTICE AND WARRANTY
HOBBS ELECTROOPTICS/ELECTROOPTICAL INNOVATIONS, LLC. PROVIDES THIS
PUBLICATION “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. (Disclaimer
of expressed or implied warranties in certain transactions is not allowed in some states.
Therefore, the above statement may not apply to you.)
This manual may contain technical inaccuracies and/or typographical errors. Changes are
periodically made to this manual which are incorporated in later editions. Hobbs Elec-
troOptics/ElectroOptical Innovations, LLC. may make changes and improvements to the
product(s) and/or programs described in this publication at any time without notice. The
QL01 has non-zero failure rates associated with its hardware, firmware, design, and docu-
mentation. Do not use the product in applications where a failure or defect in the instrument
may result in injury, loss of life, or property damage.
IN NO EVENT WILL HOBBS ELECTROOPTICS/ELECTROOPTICAL INNOVATIONS,
LLC. OR ITS MEMBERS OR EMPLOYEES BE LIABLE FOR DAMAGES, INCLUDING
LOST PROFITS, LOST SAVINGS OR OTHER INCIDENTAL OR CONSEQUENTIAL
DAMAGES ARISING OUT OF THE USE OF OR INABILITY TO USE SUCH PRODUCT,
EVEN IF HOBBS ELECTROOPTICS/ELECTROOPTICAL INNOVATIONS, LLC. OR
AN APPROVED RESELLER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
DAMAGES, OR FOR ANY CLAIM BY ANY OTHER PARTY.
ii
Contents
Contents ii
1 Introduction 1
2 Specifications 2
3 Photos 5
4 Quick Guide To Using The QL01 7
5 Theory of Operation 9
5.1 Noise In Photoreceivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.2 Shot noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.3 Transimpedance Amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.4 Bootstraps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.5 The QL01 Difference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6 Performance Verification 16
6.1 Pulse Response and Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.2 Measuring The Noise Floor Accurately . . . . . . . . . . . . . . . . . . . . . 16
6.6 Finding the Shot Noise Limit . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.3 Transient Response (Model A and B) . . . . . . . . . . . . . . . . . . . . . . 19
6.4 Model A Noise Floor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.5 Model B Noise Floor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
References 24
Table of Symbols 25
1
1 Introduction
Making good optical measurements is rarely simple, but it is particularly difficult in very
low light, as anyone knows who’s ever tried it.
Of course, it’s easier if you can get more light somehow, maybe with a brighter laser or
a larger collection aperture. That isn’t always possible, unfortunately. Chemical, biological,
and microelectronic samples are often easily damaged by cranking the illumination power
too high, for instance, and large collecting apertures are bulky and expensive.
Low light naturally requires large feedback resistors in the transimpedance amplifier in
order to reduce thermal (Johnson) noise. Decent-sized photodiodes have a lot of capacitance,
though, which in combination with those large resistors form slow RC time constants that
limit measurement speed, signal-to-noise ratio, or both.
The Hobbs ElectroOptics QL01 is a highly sensitive photoreceiver that achieves shot-noise
limited performance with very dim light, from 10 nanowatts up to a few microwatts, with
a previously unattainable combination of sensitivity and bandwidth. It uses a proprietary
bootstrap architecture to reduce the effect of photodiode capacitance by a factor of over
1000, with sub-nanovolt noise densities. This allows the Model B to offer shot-noise-limited
detection performance at 25 nA out to its full 1 MHz bandwidth, and at 8 nA in 100 kHz.
The Model A trades off a bit of low-light performance for a 7x increase in detector area for
more light collection and ease of alignment.
Low-light applications in solid state physics, spectroscopy, chemistry, biology, and other
fields will see an immediate improvement in their measurements when they switch to the
QL01. For applications with a bit more light available, forthcoming versions C and D will
extend the bandwidth to 3 MHz at 1 MΩ transimpedance. Fiber-coupled versions with
performance from 800-1700 nm are in the works as well.
These instruments are designed to survive the accidents that sometimes happen in a
research lab, with medical-grade power supplies, a thick aluminum box, a stainless steel
mounting thread, and a solid metal BNC output connector securely attached to the box
itself.
The QL01 series are the first of a family of advanced photoreceivers from Hobbs Elec-
troOptics. These are all-new designs based on expertise gained through our own research
and from designing dozens of advanced instruments for our consulting clients. We also do
specials and OEM products, so if you have an unusual requirement, give us a call or send an
email.
Philip C. D. Hobbs Hobbs ElectroOptics/ElectroOptical Innovations, LLC.
Principal 160 North State Road, Suite 203
(914) 236-3005 Briarcliff Manor, NY 10510
[email protected] http://hobbs-eo.com
Section 2: Specifications
2 Specifications
QL01 Quantum-Limited Nanowatt Photoreceiver
FUNCTION Single-channel, low noise optical to electrical converter
INPUT Free space optical detector.
PHOTOCURRENT
RANGE
QL01-A/B: 0 - 1 µA
OUTPUT BNC connector, output impedance 50 Ω (A high-Z load is
preferred, as this prevents increased photodiode leakage
due to internal power dissipation.)
WAVELENGTH QL01-A/B: <400 nm - 1100 nm.
DETECTOR AREA QL01-A: 2.65 mm square detector, 7 mm2area
QL01-B: 1 mm square detector, 1 mm2area
TRANSIMPEDANCE 10 MΩ (10 V/µA)
RESPONSIVITY 0.6 A/W typical @ 840 nm (set by the photodiode)
QUANTUM
EFFICIENCY
0.9 typical @ 840 nm, >10% 380-1080 nm (QL01-A),
350-1080 nm (QL01-B)
BANDWIDTH DC - 1 MHz @ -3 dB
RISE / FALL TIME 400 ns typical, 10% - 90%, see Figure 6.1
QL01 2
Section 2: Specifications
QL01 Quantum-Limited Nanowatt Photoreceiver
OFFSET CURRENT ±10 nA maximum @ 25◦C
NOISE
(INPUT-REFERRED)
@ 25 ◦C
QL01-A: Noise floor <60 fA/√Hz (DC - 100 kHz):
Shot noise limited above 10 nA (DC- 100 kHz) or 45 nA
(DC - 1 MHz). See Figure 6.2
QL01-B: Noise floor <60 fA/√Hz (DC - 100 kHz):
Shot noise limited above 8 nA (DC - 100 kHz) or 25 nA
in DC - 1 MHz . See Figure 6.3
NOISE EQUIVALENT
POWER (NEP)
Optical power needed to reach SNR of 1.0. At at 840
nm, the QL01-A’s 60 fA/√Hz noise current equals 75 fW
NEP in 1 Hz.
OVERSHOOT: 3% maximum, measured with an input pulse with 100 ns
time constant (See Figure 6.1)
OPERATING
TEMPERATURE
0◦C - 60◦C
Note: Photodiode leakage increases with temperature,
leading to increased DC offset voltages and more noise.
QL01 3
Section 2: Specifications
QL01 Quantum-Limited Nanowatt Photoreceiver
SHIELDING Solid extruded aluminum enclosure with die-cast alu-
minum end plates and conductive gaskets for EMI
rejection
POWER 24 V DC @ 150 mA maximum; universal 100-240 V, 50-
60 Hz medical-grade power brick supplied
INDICATOR The green LED on the back panel lights when all power
supply voltages are normal
DIMENSIONS
AND
MOUNTING
Hammond 1457L1201EBK enclosure with removable
stainless steel flange with 1/4-20 or M6-1 tapped hole
and four self-adhesive rubber feet. Flanged end plates
with mounting slots are optional.
QL01 4
Section 3: Photos
3 Photos
Figure 3.1: Top view of the instrument
Figure 3.2: Bottom view showing 1-3/4” mounting flange with 1/4”-20 or M6 threaded
mounting hole
QL01 5
Section 3: Photos
Figure 3.3: End view showing power connector, power indicator LED, and output BNC
QL01 6
Este manual sirve para los siguientes modelos
2
Tabla de contenidos
