Quantum Limited Photoreceiver

The QL01-A/B are the first of a family of advanced photoreceivers from Hobbs ElectroOptics. Offering a previously unattainable combination of low noise and high speed, they allow measurements at the quantum (shot noise) sensitivity limit in a full 1 MHz bandwidth at light levels from as low as 35 nanowatts up to a few microwatts.

The QL01s 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 other OEM products, so if you have an unusual requirement, give us a call or send an email.


Built to withstand lab accidents with a thick aluminum box, a stainless steel mounting thread, and a solid metal BNC output connector securely attached to the box itself.

With a quantum-limited photoreceiver, the signal-to-noise ratio of the measurement is just that of the light itself -- all the information present in your optical signal is preserved for the measurement. Typically we're working pretty hard to get that signal, so it's a shame to let a poor photoreceiver degrade it. That's where the QL01 comes in.

Competing products may reach this level near DC, but none beyond 10 kHz, a full factor of 100 slower than the QL01. Why should you care about speed? First of all, with 100 times the bandwidth and the same noise level, you get 100 times more data. More subtly, you can do your measurement further from DC, where many sources of noise and interference are much less troublesome. The QL01 photoreceiver is only $850, which is generally a small part of the total system cost. Why not choose the best?

The QL01 achieves its outstanding performance through a proprietary bootstrap topology that reduces the effect of photodiode capacitance by a factor of over 1000, with sub-nanovolt noise densities. This advanced design gives the Model B shot-noise-limited detection performance at 25 nA out to its full 1~MHz bandwidth, and at 7 nA in 100 kHz.

The Model A trades off a bit of low-light performance to gain a 7x increase in detector area for more light collection and ease of alignment: it is quantum limited above 45 nA in 1 MHz and above 8 nA in 100 kHz. 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. The QL01 is also available in an OEM version, ready to bring improved sensitivity to commercial instruments.

The standard 1/4-20" stainless steel mounting thread and the QL01's relatively large photodiodes allow for simple mounting and alignment.

Specification Highlights

Model A Model B
Bandwidth DC - 1 MHz DC - 1 MHz
Rise/Fall Time 400 ns 400 ns
Transimpedance 10 MΩ 10 MΩ
Output Voltage 0 - 10 V 0 - 10 V
Integrated Noise (DC-1MHz) 1.1 mV 0.8 mV
Slew Rate No slew limiting with full scale step input No slew limiting with full scale step input


QL01 Product Announcement

QL01 User Manual

Price and Ordering

The QL01-A/B are both $850 (quantity 1-5) and are usually shipped from stock. To order, fill out our Product Order Form or send us an email at orders@hobbs-eo.com

We also do specials and other OEM products, so if you have an unusual requirement, give us a call or send an email.